diff --git a/core/includes/form.inc b/core/includes/form.inc
index 5f580fb..fde5712 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -2804,6 +2804,39 @@ function theme_fieldset($variables) {
 }
 
 /**
+ * Returns HTML for a details form element and its children.
+ *
+ * @param $variables
+ *   An associative array containing:
+ *   - element: An associative array containing the properties of the element.
+ *     Properties used: #attributes, #children, #collapsed, #collapsible,
+ *     #description, #id, #title, #value.
+ *
+ * @ingroup themeable
+ */
+function theme_details($variables) {
+  $element = $variables['element'];
+  element_set_attributes($element, array('id'));
+  _form_set_class($element, array('form-wrapper'));
+
+  $output = '<details' . drupal_attributes($element['#attributes']) . '>';
+  if (!empty($element['#title'])) {
+    $output .= '<summary>' . $element['#title'] . '</summary>';
+  }
+  $output .= '<div class="details-wrapper">';
+  if (!empty($element['#description'])) {
+    $output .= '<div class="details-description">' . $element['#description'] . '</div>';
+  }
+  $output .= $element['#children'];
+  if (isset($element['#value'])) {
+    $output .= $element['#value'];
+  }
+  $output .= '</div>';
+  $output .= "</details>\n";
+  return $output;
+}
+
+/**
  * Returns HTML for a radio button form element.
  *
  * Note: The input "name" attribute needs to be sanitized before output, which
@@ -3695,6 +3728,40 @@ function form_process_fieldset(&$element, &$form_state) {
 }
 
 /**
+ * Arranges details into groups.
+ *
+ * @param $element
+ *   An associative array containing the properties and children of the
+ *   details. Note that $element must be taken by reference here, so processed
+ *   child elements are taken over into $form_state.
+ * @param $form_state
+ *   The $form_state array for the form this details belongs to.
+ *
+ * @return
+ *   The processed element.
+ */
+function form_process_details(&$element, &$form_state) {
+  $parents = implode('][', $element['#parents']);
+
+  // Each detail forms a new group. The #type 'vertical_tabs' basically only
+  // injects a new details element.
+  $form_state['groups'][$parents]['#group_exists'] = TRUE;
+  $element['#groups'] = &$form_state['groups'];
+
+  // Process vertical tabs group member details.
+  if (isset($element['#group'])) {
+    // Add this details to the defined group (by reference).
+    $group = $element['#group'];
+    $form_state['groups'][$group][] = &$element;
+  }
+
+  // Contains form element summary functionalities.
+  $element['#attached']['library'][] = array('system', 'drupal.form');
+
+  return $element;
+}
+
+/**
  * Adds members of this group as actual elements for rendering.
  *
  * @param $element
@@ -3766,6 +3833,77 @@ function form_pre_render_fieldset($element) {
 }
 
 /**
+ * Adds members of this group as actual elements for rendering.
+ *
+ * @param $element
+ *   An associative array containing the properties and children of the
+ *   details.
+ *
+ * @return
+ *   The modified element with all group members.
+ */
+function form_pre_render_details($element) {
+  // The .form-wrapper class is required for #states to treat details like
+  // containers.
+  if (!isset($element['#attributes']['class'])) {
+    $element['#attributes']['class'] = array();
+  }
+
+  // Collapsible details
+  if (!empty($element['#collapsible'])) {
+    $element['#attached']['library'][] = array('system', 'drupal.collapse');
+    $element['#attributes']['class'][] = 'collapsible';
+    if (!empty($element['#collapsed'])) {
+      $element['#attributes']['class'][] = 'collapsed';
+    }
+  }
+
+  // Fieldsets may be rendered outside of a Form API context.
+  if (!isset($element['#parents']) || !isset($element['#groups'])) {
+    return $element;
+  }
+  // Inject group member elements belonging to this group.
+  $parents = implode('][', $element['#parents']);
+  $children = element_children($element['#groups'][$parents]);
+  if (!empty($children)) {
+    foreach ($children as $key) {
+      // Break references and indicate that the element should be rendered as
+      // group member.
+      $child = (array) $element['#groups'][$parents][$key];
+      $child['#group_details'] = TRUE;
+      // Inject the element as new child element.
+      $element[] = $child;
+
+      $sort = TRUE;
+    }
+    // Re-sort the element's children if we injected group member elements.
+    if (isset($sort)) {
+      $element['#sorted'] = FALSE;
+    }
+  }
+
+  if (isset($element['#group'])) {
+    $group = $element['#group'];
+    // If this element belongs to a group, but the group-holding element does
+    // not exist, we need to render it (at its original location).
+    if (!isset($element['#groups'][$group]['#group_exists'])) {
+      // Intentionally empty to clarify the flow; we simply return $element.
+    }
+    // If we injected this element into the group, then we want to render it.
+    elseif (!empty($element['#group_details'])) {
+      // Intentionally empty to clarify the flow; we simply return $element.
+    }
+    // Otherwise, this element belongs to a group and the group exists, so we do
+    // not render it.
+    elseif (element_children($element['#groups'][$group])) {
+      $element['#printed'] = TRUE;
+    }
+  }
+
+  return $element;
+}
+
+/**
  * Creates a group formatted as vertical tabs.
  *
  * @param $element
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 429e990..0ca1001 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -1609,7 +1609,7 @@ function system_performance_settings($form, &$form_state) {
   );
 
   $form['caching'] = array(
-    '#type' => 'fieldset',
+    '#type' => 'details',
     '#title' => t('Caching'),
   );
 
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index d1c314d..147c526 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -530,6 +530,14 @@ function system_element_info() {
     '#pre_render' => array('form_pre_render_fieldset'),
     '#theme_wrappers' => array('fieldset'),
   );
+  $types['details'] = array(
+    '#collapsible' => FALSE,
+    '#collapsed' => FALSE,
+    '#value' => NULL,
+    '#process' => array('form_process_details', 'ajax_process_form'),
+    '#pre_render' => array('form_pre_render_details'),
+    '#theme_wrappers' => array('details'),
+  );
   $types['vertical_tabs'] = array(
     '#theme_wrappers' => array('vertical_tabs'),
     '#default_tab' => '',