Answer:
Lots of them make up a word, And lots of words are in them. It's easy when you think about it. A while ago we stamped and mailed them.
I'm a green veggie that looks like a tiny tree.
What building has the most stories?
You're currently trying to solve one
Some adults still use these to count.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.