diff --git a/THEME.md b/THEME.md
new file mode 100644
index 00000000..46cad0e6
--- /dev/null
+++ b/THEME.md
@@ -0,0 +1,169 @@
+This document describes how Terminology interacts with themes and what needs
+to be handled by themes.
+
+See `ChangeLog.theme` on changes related to themes.
+
+
+Windows contain group `terminology/base`.
+
+
+# `terminology/base`
+Contains what is global to a window.
+
+## Swallowed parts
+
+### `terminology.content`
+where `terminology/background`, or a split widget can be swallowed.
+
+### `terminology.cmdbox`
+To swallow a command box.
+It reacts to the following signals:
+* `cmdbox,show`
+* `cmdbox,hide`
+
+### `terminology.about`
+It reacts to the following signals:
+* `about,show`
+* `about,hide`
+
+### `terminology.optdetails`
+Detailed settings panel.
+It reacts to the following signals:
+* `optdetails,show`
+* `optdetails,hide`
+It emits the following signal:
+* `optdetails,hide,done`
+
+### `terminology.options`
+It reacts to the following signals:
+* `options,show`
+* `options,hide`
+
+### `terminology.controls`
+The controls box shown on right click.
+It reacts to the following signals:
+* `controls,show`
+* `controls,hide`
+
+
+
+# `terminology/background`
+
+## Swallowed parts
+
+### `terminology.content`
+Here is swallowed an object of group `terminology.background`.
+
+__TODO__
+
+
+
+# `terminology/core`
+
+## Swallowed parts
+
+### `terminology.background`
+
+Actual background.
+It reacts to the following signals based on the media to play in background:
+* `media,off`
+* `media,image`
+* `media,scale`
+* `media,edje`
+* `media,movie`
+
+### `terminology.tabregion`
+Here is swalloed a fully transparent rectangle to move down the textgrid.
+
+### `terminology.content`
+Where actual text grid goes.
+
+## Signal received
+### `tabbar,off` and `tabbar,on`
+Whether to display a tab bar. Default is off.
+### `tab_btn,off` and `tab_btn,on`
+Whether to display a tab button to easily navigate through tabs. Default is off.
+
+
+
+# `terminology/about`
+## Text parts
+### `terminology.text`
+The text of the __About__ message.
+
+
+
+# `terminology.tabbar_back`
+An inactive tab item
+## Text parts
+### `terminology.title`
+Title of the tab.
+
+## Signal emitted
+### `tab,activate`
+When clicked on it, to notify that the user wants to go to that tab.
+
+## Signal received
+### `bell`
+To mark the tab as having received a bell.
+
+
+
+# `terminology/keybinding`
+__TODO__
+
+
+
+# `terminology/miniview`
+__TODO__
+
+
+
+# `terminology/fontpreview`
+__TODO__
+
+
+
+# `terminology/selection`
+An object used when selecting text.
+__TODO__
+
+
+
+# `terminology/cursor`
+__TODO__
+
+
+
+# `terminology/cursor_bar`
+__TODO__
+
+
+
+# `terminology/cursor_underline`
+__TODO__
+
+
+
+# `terminology/sel/base`
+__TODO__
+
+
+
+# `terminology/sel/item`
+__TODO__
+
+
+
+# `terminology/link`
+An object overlayd on text that is a link.
+
+
+
+# `terminology/mediabusy`
+__TODO__
+
+
+
+# `terminology/mediactrl`
+__TODO__