GUI.Label with down symbols

Good afternoon. By application programming I had a question. How to display the lower characters in one GUI.Label ()? For example, I want to see a water formula on the screen: H2O where number 2 - is see as the lower character. Thanks in advance for the help.

Subscript numbers exist as Unicode characters, so you can type it in as text: H₂O. (On OS X, use the character palette with Symbols → Numbers and Number Symbols.)