By chaining the selectors together, he was able to encode invisible messages inside an emoji (or any other Unicode character). Here is how it works: Unicode assigns variation selectors (U+FE00–U+FE0F ...

Paul Butler tests and demonstrates the flexibility of encoding hidden messages within Unicode characters, including emoji.

In version 7.0, Unicode also comes with documentation for 250 new emoji characters. Emojipedia has a list of the names chosen for the new emoji, which include “Wind Blowing Face”, “National Park”, ...