Answer:
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
I'm the source of all emotion, but I'm caged in a white prison.
What has roots that nobody sees, and is taller than trees. Up, up it goes, and yet it never grows.
What starts with a P, ends with an E and has a million letters in it?
What is in seasons, seconds, centuries, and minutes, but not in decades, years, or days?
What never gets any wetter no matter how hard it rains?