Tapping the smiling face icon displays the emoji set and replaces the icon with the keyboard icon. Tapping the keyboard icon hides the emoji set and shows the keyboard, if the device does not have a physical keybord. All emoticons are split to categories (marked by the category icons). The categories have vertical scroll.
When tapped, the emoticon is inserted inside the input text field. Emoji display must be supported in all chats, chat lists and notifications, as well as contact names and group titles.
You can download the full emoji set split by categories here: emoji.zip (Download).