Answer:
I am commonly abbreviated to H
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair.
I begin your sentences.
When it comes to me, you go on red and stops on green. What am I?
What two things can you never eat for breakfast?
What never gets any wetter no matter how hard it rains?
What am I?
Animal
Difficult
Easy
Food
Funny
Kids
Logic