Answer:
A time when they're green. A time when they're brown. But both of these times, cause me to frown. But just in between, for a very short while. They're perfect and yellow. And cause me to smile.
What begins and has no end? What is the ending of all that begins?
What is the only letter in the alphabet that does not appear anywhere on the periodic table of elements?
Look into my face and I'm everybody. Scratch my back and I'm nobody.
My first is in some but not in all. My second is into but not in tall. My third in little but no in big. My fourth in port but not in pig. My whole is made in nature's way. For clothing, rugs used every day.
You use it between your head and your toes, the more it works the thinner it grows.