diff --git a/superset/assets/src/CRUD/CollectionTable.jsx b/superset/assets/src/CRUD/CollectionTable.jsx
index ffe0733ef8..00b3a0b2b9 100644
--- a/superset/assets/src/CRUD/CollectionTable.jsx
+++ b/superset/assets/src/CRUD/CollectionTable.jsx
@@ -23,7 +23,7 @@ import { t } from '@superset-ui/translation';
 import Button from '../components/Button';
 import Fieldset from './Fieldset';
 import { recurseReactClone } from './utils';
-import './styles.css';
+import './crud.less';
 
 const propTypes = {
   collection: PropTypes.arrayOf(PropTypes.object).isRequired,
diff --git a/superset/assets/src/CRUD/Field.jsx b/superset/assets/src/CRUD/Field.jsx
index 4ef0330088..902b68199b 100644
--- a/superset/assets/src/CRUD/Field.jsx
+++ b/superset/assets/src/CRUD/Field.jsx
@@ -22,7 +22,7 @@ import {
   FormGroup, ControlLabel, HelpBlock, FormControl, OverlayTrigger, Tooltip,
 } from 'react-bootstrap';
 
-import './styles.less';
+import './crud.less';
 
 const propTypes = {
   value: PropTypes.any.isRequired,
diff --git a/superset/assets/src/CRUD/styles.css b/superset/assets/src/CRUD/crud.less
similarity index 65%
rename from superset/assets/src/CRUD/styles.css
rename to superset/assets/src/CRUD/crud.less
index 6b0484b84a..af1838e959 100644
--- a/superset/assets/src/CRUD/styles.css
+++ b/superset/assets/src/CRUD/crud.less
@@ -16,17 +16,32 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-.CRUD i.fa-caret-down,
-i.fa-caret-up {
-  width: "5px";
-}
-.CRUD td.expanded {
-  border-top: "0px";
-  padding: "0px";
-}
-.CRUD .frame {
-  border: "1px solid #AAA";
-  border-radius: 5;
-  padding: 10;
-  background: "#F4F4F4";
+.CRUD {
+  .text-right {
+    text-align: right;
+  }
+  .empty-collection {
+    padding: 10px;
+  }
+  .control-label {
+    font-weight: bold;
+    font-size: 16px;
+  }
+  .tiny-cell {
+    width: 5px;
+  }
+  i.fa-caret-down,
+  i.fa-caret-up {
+    width: "5px";
+  }
+  td.expanded {
+    border-top: "0px";
+    padding: "0px";
+  }
+  .frame {
+    border: "1px solid #AAA";
+    border-radius: 5;
+    padding: 10;
+    background: "#F4F4F4";
+  }
 }
diff --git a/superset/assets/src/CRUD/styles.less b/superset/assets/src/CRUD/styles.less
deleted file mode 100644
index 6c191521f5..0000000000
--- a/superset/assets/src/CRUD/styles.less
+++ /dev/null
@@ -1,32 +0,0 @@
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-.CRUD .text-right {
-  text-align: right;
-}
-.CRUD .empty-collection {
-  padding: 10px;
-}
-.CRUD .control-label {
-  font-weight: bold;
-  font-size: 16px;
-}
-
-.CRUD .tiny-cell {
-  width: 5px;
-}
diff --git a/superset/assets/src/chart/Chart.jsx b/superset/assets/src/chart/Chart.jsx
index b2791cf8bf..a29079a2ff 100644
--- a/superset/assets/src/chart/Chart.jsx
+++ b/superset/assets/src/chart/Chart.jsx
@@ -27,7 +27,7 @@ import RefreshChartOverlay from '../components/RefreshChartOverlay';
 import StackTraceMessage from '../components/StackTraceMessage';
 import ErrorBoundary from '../components/ErrorBoundary';
 import ChartRenderer from './ChartRenderer';
-import './chart.css';
+import './chart.less';
 
 const propTypes = {
   annotationData: PropTypes.object,
diff --git a/superset/assets/src/chart/chart.css b/superset/assets/src/chart/chart.less
similarity index 100%
rename from superset/assets/src/chart/chart.css
rename to superset/assets/src/chart/chart.less
diff --git a/superset/assets/src/components/FilterBadgeIcon.less b/superset/assets/src/components/FilterBadgeIcon.less
index b31848ffd7..8b6b7c65d4 100644
--- a/superset/assets/src/components/FilterBadgeIcon.less
+++ b/superset/assets/src/components/FilterBadgeIcon.less
@@ -28,12 +28,7 @@
     fill: @lightest;
   }
 }
-.filter-badge:hover {
-  cursor: pointer;
-  background-color: @gray;
-}
-
-.color-bar.badge-group,
+.filter-badge .color-bar.badge-group,
 .filter-badge.badge-group {
   background-color: @gray-dark;
 }
diff --git a/superset/assets/src/components/Loading.jsx b/superset/assets/src/components/Loading.jsx
index 5c132d9c1b..3fb5bdea76 100644
--- a/superset/assets/src/components/Loading.jsx
+++ b/superset/assets/src/components/Loading.jsx
@@ -19,7 +19,7 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 
-import './Loading.css';
+import './Loading.less';
 
 const propTypes = {
   size: PropTypes.number,
diff --git a/superset/assets/src/components/Loading.css b/superset/assets/src/components/Loading.less
similarity index 100%
rename from superset/assets/src/components/Loading.css
rename to superset/assets/src/components/Loading.less
diff --git a/superset/assets/src/components/TableSelector.jsx b/superset/assets/src/components/TableSelector.jsx
index f2111b2fde..58c9018b6e 100644
--- a/superset/assets/src/components/TableSelector.jsx
+++ b/superset/assets/src/components/TableSelector.jsx
@@ -25,7 +25,7 @@ import { SupersetClient } from '@superset-ui/connection';
 
 import AsyncSelect from './AsyncSelect';
 import RefreshLabel from './RefreshLabel';
-import './TableSelector.css';
+import './TableSelector.less';
 
 const propTypes = {
   dbId: PropTypes.number.isRequired,
diff --git a/superset/assets/src/components/TableSelector.css b/superset/assets/src/components/TableSelector.less
similarity index 93%
rename from superset/assets/src/components/TableSelector.css
rename to superset/assets/src/components/TableSelector.less
index 078e57df55..6c508c1a62 100644
--- a/superset/assets/src/components/TableSelector.css
+++ b/superset/assets/src/components/TableSelector.less
@@ -16,6 +16,8 @@
  * specific language governing permissions and limitations
  * under the License.
  */
+@import "../../stylesheets/less/variables.less";
+
 .TableSelector .fa-refresh {
   padding-left: 9px;
 }
@@ -33,7 +35,7 @@
   flex-grow: 1;
 }
 .TableSelector .divider {
-  border-bottom: 1px solid #f2f2f2;
+  border-bottom: 1px solid @gray-bg;
   margin: 15px 0;
 }
 .TableLabel {
diff --git a/superset/assets/src/explore/components/Control.jsx b/superset/assets/src/explore/components/Control.jsx
index b8babc709b..fbb74a1989 100644
--- a/superset/assets/src/explore/components/Control.jsx
+++ b/superset/assets/src/explore/components/Control.jsx
@@ -19,7 +19,7 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 
-import './Control.css';
+import './Control.less';
 import controlMap from './controls';
 
 const controlTypes = Object.keys(controlMap);
diff --git a/superset/assets/src/explore/components/Control.css b/superset/assets/src/explore/components/Control.less
similarity index 100%
rename from superset/assets/src/explore/components/Control.css
rename to superset/assets/src/explore/components/Control.less
diff --git a/superset/assets/src/explore/components/controls/CollectionControl.jsx b/superset/assets/src/explore/components/controls/CollectionControl.jsx
index 35390e97f8..57aee461cd 100644
--- a/superset/assets/src/explore/components/controls/CollectionControl.jsx
+++ b/superset/assets/src/explore/components/controls/CollectionControl.jsx
@@ -27,7 +27,7 @@ import {
 import InfoTooltipWithTrigger from '../../../components/InfoTooltipWithTrigger';
 import ControlHeader from '../ControlHeader';
 import controlMap from './';
-import './CollectionControl.css';
+import './CollectionControl.less';
 
 const propTypes = {
   name: PropTypes.string.isRequired,
diff --git a/superset/assets/src/explore/components/controls/CollectionControl.css b/superset/assets/src/explore/components/controls/CollectionControl.less
similarity index 100%
rename from superset/assets/src/explore/components/controls/CollectionControl.css
rename to superset/assets/src/explore/components/controls/CollectionControl.less
diff --git a/superset/assets/src/explore/components/controls/DateFilterControl.jsx b/superset/assets/src/explore/components/controls/DateFilterControl.jsx
index dcdf4169f1..67fb9018ac 100644
--- a/superset/assets/src/explore/components/controls/DateFilterControl.jsx
+++ b/superset/assets/src/explore/components/controls/DateFilterControl.jsx
@@ -39,7 +39,7 @@ import 'react-datetime/css/react-datetime.css';
 import moment from 'moment';
 import { t } from '@superset-ui/translation';
 
-import './DateFilterControl.css';
+import './DateFilterControl.less';
 import ControlHeader from '../ControlHeader';
 import PopoverSection from '../../../components/PopoverSection';
 
diff --git a/superset/assets/src/explore/components/controls/DateFilterControl.css b/superset/assets/src/explore/components/controls/DateFilterControl.less
similarity index 100%
rename from superset/assets/src/explore/components/controls/DateFilterControl.css
rename to superset/assets/src/explore/components/controls/DateFilterControl.less
diff --git a/superset/assets/src/explore/components/controls/VizTypeControl.jsx b/superset/assets/src/explore/components/controls/VizTypeControl.jsx
index 2970a93fc6..3be9378835 100644
--- a/superset/assets/src/explore/components/controls/VizTypeControl.jsx
+++ b/superset/assets/src/explore/components/controls/VizTypeControl.jsx
@@ -26,7 +26,7 @@ import { t } from '@superset-ui/translation';
 import { getChartMetadataRegistry } from '@superset-ui/chart';
 
 import ControlHeader from '../ControlHeader';
-import './VizTypeControl.css';
+import './VizTypeControl.less';
 
 const propTypes = {
   description: PropTypes.string,
diff --git a/superset/assets/src/explore/components/controls/VizTypeControl.css b/superset/assets/src/explore/components/controls/VizTypeControl.less
similarity index 100%
rename from superset/assets/src/explore/components/controls/VizTypeControl.css
rename to superset/assets/src/explore/components/controls/VizTypeControl.less
diff --git a/superset/assets/src/showSavedQuery/index.jsx b/superset/assets/src/showSavedQuery/index.jsx
index c64626cb6a..b5ef27a77e 100644
--- a/superset/assets/src/showSavedQuery/index.jsx
+++ b/superset/assets/src/showSavedQuery/index.jsx
@@ -20,7 +20,7 @@ import React from 'react';
 import ReactDom from 'react-dom';
 import Form from 'react-jsonschema-form';
 import { interpolate } from 'src/showSavedQuery/utils';
-import './index.css';
+import './index.less';
 
 const scheduleInfoContainer = document.getElementById('schedule-info');
 const bootstrapData = JSON.parse(scheduleInfoContainer.getAttribute('data-bootstrap'));
diff --git a/superset/assets/src/showSavedQuery/index.css b/superset/assets/src/showSavedQuery/index.less
similarity index 100%
rename from superset/assets/src/showSavedQuery/index.css
rename to superset/assets/src/showSavedQuery/index.less
diff --git a/superset/assets/src/visualizations/TimeTable/TimeTable.jsx b/superset/assets/src/visualizations/TimeTable/TimeTable.jsx
index c895d46187..50415696d9 100644
--- a/superset/assets/src/visualizations/TimeTable/TimeTable.jsx
+++ b/superset/assets/src/visualizations/TimeTable/TimeTable.jsx
@@ -29,7 +29,7 @@ import MetricOption from '../../components/MetricOption';
 import InfoTooltipWithTrigger from '../../components/InfoTooltipWithTrigger';
 import FormattedNumber from './FormattedNumber';
 import SparklineCell from './SparklineCell';
-import './TimeTable.css';
+import './TimeTable.less';
 
 const ACCESSIBLE_COLOR_BOUNDS = ['#ca0020', '#0571b0'];
 
diff --git a/superset/assets/src/visualizations/TimeTable/TimeTable.css b/superset/assets/src/visualizations/TimeTable/TimeTable.less
similarity index 100%
rename from superset/assets/src/visualizations/TimeTable/TimeTable.css
rename to superset/assets/src/visualizations/TimeTable/TimeTable.less
diff --git a/superset/assets/stylesheets/explore.less b/superset/assets/stylesheets/explore.less
deleted file mode 100644
index de48b89897..0000000000
--- a/superset/assets/stylesheets/explore.less
+++ /dev/null
@@ -1,43 +0,0 @@
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-@import "../stylesheets/less/variables.less";
-
-.widget {
-    position: relative;
-}
-
-.slice_container {
-    position: absolute;
-    left: 0;
-    top: 0;
-    background-color: @lightest;
-}
-
-.navbar {
-  margin-bottom: 22px;
-}
-
-.query-and-save-btns-container {
-  margin-bottom: 22px;
-}
-
-.star-edit-icons {
-  padding-left: 10px;
-  font-size: 50%;
-}
diff --git a/superset/assets/stylesheets/profile.css b/superset/assets/stylesheets/profile.css
deleted file mode 100644
index 117e88a0b9..0000000000
--- a/superset/assets/stylesheets/profile.css
+++ /dev/null
@@ -1,21 +0,0 @@
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-.table i {
-  padding-top: 6px;
-}
diff --git a/superset/assets/stylesheets/sql.less b/superset/assets/stylesheets/sql.less
deleted file mode 100644
index ca7e56b2da..0000000000
--- a/superset/assets/stylesheets/sql.less
+++ /dev/null
@@ -1,61 +0,0 @@
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-@import "../stylesheets/less/variables.less";
-
-.topsql {
-  height: 250px;
-}
-.dataTables_filter {
-  padding-top: 5px;
-  padding-right: 5px;
-}
-.bordered {
-  padding: 0px 0px;
-  border: 1px solid @gray;
-  border-radius: 5px;
-  background-color: @gray-bg;
-}
-div.alert {
-  padding: 5px;
-  margin: 0px;
-}
-.metadata {
-  overflow: auto;
-  width: 300px;
-  height: 100px;
-}
-.fillup {
-  width: 100%;
-  height: 100%;
-}
-.fillheight {
-  height: 100%;
-}
-.interactions {
-  padding-bottom: 10px;
-}
-#results {
-  overflow: auto;
-  font-size: 12px;
-  margin-bottom: 5px;
-}
-table tbody tr td {
-  padding: 1px 4px;
-  font-size: small;
-}
diff --git a/superset/assets/stylesheets/welcome.less b/superset/assets/stylesheets/welcome.less
deleted file mode 100644
index cb51649d39..0000000000
--- a/superset/assets/stylesheets/welcome.less
+++ /dev/null
@@ -1,55 +0,0 @@
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-@import "../stylesheets/less/variables.less";
-
-.table i {
-  padding-top: 6px;
-}
-
-img.loading {
-  width: 25px;
-}
-
-.welcome table {
-    display: none;
-    width: 100%;
-}
-
-input {
-    margin-left: 5px;
-    margin-top: 8px;
-}
-
-.panel-body {
-    overflow: auto;
-}
-
-.cal-heatmap-panel {
-  padding: 20px;
-  background-color: @lightest;
-}
-.search input {
-  width: 400px;
-}
-.search-container .fa-search {
-  float: left;
-  margin-left: -25px;
-  margin-top: 12px;
-  font-size: 18px;
-}