diff --git a/block_groups.php b/block_groups.php
index f09b046..5b4476b 100644
--- a/block_groups.php
+++ b/block_groups.php
@@ -187,12 +187,38 @@ public function build_grouping_array($allgroupings, $courseid) {
                     $countgroupingmember = $arrayofmembers[$value->id]->number;
                 }
 
-                $groupingsarray[$g] = $renderer->get_grouping($value, $countgroupingmember);
+                $groupnames = $this->get_groups_for_grouping($value->id, $courseid);
+
+                $groupingsarray[$g] = $renderer->get_grouping($value, $countgroupingmember, $groupnames);
             }
         }
         return $groupingsarray;
     }
 
+    /**
+     * Returns the names of all groups belonging to a grouping.
+     *
+     * @param integer $groupingid
+     * @param integer $courseid
+     * @return array
+     * @throws dml_exception
+     */
+    private function get_groups_for_grouping($groupingid, $courseid) {
+        global $DB;
+
+        $sql = "SELECT g.id, g.name
+              FROM {groups} g
+              JOIN {groupings_groups} gg ON gg.groupid = g.id
+             WHERE gg.groupingid = :groupingid
+               AND g.courseid = :courseid
+          ORDER BY g.name ASC";
+
+        return $DB->get_records_sql($sql, [
+                'groupingid' => $groupingid,
+                'courseid' => $courseid,
+        ]);
+    }
+
     /**
      * Tells moodle, that the groups block has a settings file.
      * @return bool true
diff --git a/classes/output/renderer.php b/classes/output/renderer.php
index 11563d2..f99e0ba 100644
--- a/classes/output/renderer.php
+++ b/classes/output/renderer.php
@@ -41,9 +41,14 @@ public function teaching_groups_or_groupings_list($elementarray, $group) {
         } else {
             $type = 'grouping';
         }
-        $contentgroups = html_writer::tag('input', '', ['type' => "checkbox", 'value' => "1",
-                'class' => "blockgroupsandgroupingcheckbox", 'id' => 'checkbox' . $type]) .
-            html_writer::tag('label', get_string($type, 'block_groups'), ['for' => "checkbox" . $type]);
+        $labeltext = get_string($type, 'block_groups') . ' (' . count($elementarray) . ')';
+        $contentgroups = html_writer::tag('input', '', [
+                'type' => "checkbox",
+                'value' => "1",
+                'class' => "blockgroupsandgroupingcheckbox",
+                'id' => 'checkbox' . $type,
+            ]) .
+            html_writer::tag('label', $labeltext, ['for' => "checkbox" . $type]);
         $contentgroups .= html_writer::alist($elementarray, ['class' => 'wrapperlist' . $type]);
         return html_writer::tag('div', $contentgroups, ['class' => 'wrapperblockgroupsandgroupingcheckbox']);
     }
@@ -90,13 +95,17 @@ public function get_string_group($value, $href, $countmembers, $visibility) {
                 'data-action' => $action]);
         return html_writer::span($line, 'group-' . $value->id);
     }
+
     /**
      * Generates string for a grouping list item
+     *
      * @param stdClass $grouping
      * @param integer $counter
-     * @return string html-string
+     * @param array $groups
+     * @return string
+     * @throws \coding_exception
      */
-    public function get_grouping($grouping, $counter) {
+    public function get_grouping($grouping, $counter, $groups = []) {
         $line = html_writer::span(
             $grouping->name . '   ' . get_string('brackets', 'block_groups', $counter),
             'wrapperblockgroupsgrouping'
@@ -105,7 +114,18 @@ public function get_grouping($grouping, $counter) {
         $showlink = $this->create_grouping_link('show', $grouping->id, false);
         $hidelink = $this->create_grouping_link('hide', $grouping->id, false);
 
-        return html_writer::span($line . $showlink . $hidelink, 'grouping-' . $grouping->id);
+        if (!empty($groups)) {
+            $groupitems = [];
+
+            foreach ($groups as $group) {
+                $groupitems[] = s($group->name);
+            }
+            $groupslist = html_writer::alist($groupitems, [
+                    'class' => 'wrapperlistgroupinggroups',
+            ]);
+        }
+
+        return html_writer::span($line . $showlink . $hidelink . $groupslist, 'grouping-' . $grouping->id);
     }
     /**
      * Renders line to change all groups.
diff --git a/styles.css b/styles.css
index 13b7653..ea17e8b 100644
--- a/styles.css
+++ b/styles.css
@@ -48,3 +48,29 @@
 .block_groups .block-groups-spinner {
     padding-right: 6px;
 }
+
+.block_groups input.blockgroupsandgroupingcheckbox {
+    cursor: pointer;
+    display: none;
+    text-align: left;
+}
+
+.block_groups input.blockgroupsandgroupingcheckbox ~ label {
+    cursor: pointer;
+}
+
+.block_groups input.blockgroupsandgroupingcheckbox ~ label::before {
+    content: "▸";
+    display: inline-block;
+    width: 0.8em;
+    margin-right: 0.2rem;
+    font-size: 1.5em;
+}
+
+.block_groups input.blockgroupsandgroupingcheckbox:checked ~ label::before {
+    content: "▾";
+}
+
+.block_groups .wrapperlistgroupinggroups {
+    opacity: 0.85;
+}
\ No newline at end of file