What is a tiny green bug that can fly and has see through wings?

There is little information to work with, but if it is a little bigger than a grain of sand and slow moving it is probably an aphid, possibly a green Apple aphid.

If it is iridescent green it might either bee a soldier bee or a hoverfly.

If it is a couple inches long and very narrow it is probably a damselfly, a relative of the dragonfly.