Microscopes are useful tools to use to teach your children about science. Expensive microscope can be an overkill though. The GeoSafari Jr. My First Microscope is a cute product that lets small kids see small objects they find all around them. It works for rocks, coin, and everything in between. The device offers 8x magnification, a LED light, and non-skid feet.
This scientific tool runs on 3 batteries. It has a large, fixed sample tray, ideal for bugs, rocks, and everything in between. Costs under $20 at this time.