I thought this tiny greenish spider was a sheet-web weaver, but thanks to the good folk at Bug Guide, I now know it is an orb weaver (Araneidae). It is so tiny and the shape is so much like a sheet-web weaver, that I would never have guessed what it really is. This shows three views of it, from the back showing the striped abdomen, from the side, and one shot of its underside.