I grew up out in the country. There was a big pile of gravel near my house that my brother and I were always told not to play on. So of course, the gravel pile was a continual source of fascination, and I spent a lot of time out there. At some point, my brother and I discovered that there were lots of tiny fossils mixed in with the bits of gravel, and I have collected quite a few. The most common ones are the round or cylindrical fossils of crinoids.