The emoji or emoticon were already quite numerous on the previous version of Android but since the arrival of Jelly Bean (4.1 and 4.2) is the big bamboo in your SMS. To turn them on, go to Settings> Language & Input and click the settings button on the keyboard you are using. Then go to the Additional Dictionaries section and install the one named "Emoji for English words". You can now add emoji instead of some words like "flake" or "boat".

**Lists Emoji / Unicode shortcuts for the Android stock keyboard.

Make a heart in emoji
Version 4.2 (JellyBean) of Android brought to our smartphones the support of emojis. These are icons, colorful, very popular in Japan and brought to the attention of the very large European audience by Apple with iOS.

In reality we are not dealing with real emojis, but with Unicode characters (v5 / v6). From this observation follows four consequences, important to understand:
The characters are monochrome
The characters must be in the font chosen for the interface.
24-bit characters like the pictogram "fire"  are viewable, copyable and collapsible. Only unicode characters 8 and 16 bits are managed by the dictionary.
REAL emojis are not managed by Android based (but some ROMs like CyanogenMod know how to display them).