Leeuwenhoek's microscopes were simple but surprisingly powerful devices that could magnify objects 250 times or more. Peering through his signature tiny glass lens with light from a candle or the sun, he was the first to describe blood cells, some bacteria, sperm cells, muscle fibers and countless single-celled microorganisms, such as rotifers, algae, Vorticella, and Giardia.
A replica of a brass van Leeuwenhoek microscope. Image source here.
It's amazing to me that van Leeuwenhoek's microscope designs are simple to make for yourself. Excellent instructions have been written up by Patrick Keeling and posted here.
Keeling's DIY van Leeuwenhoek microscope. Image source here.
To make your own lens, you'll need some glass. Keeling's instructions suggest using a glass capillary tube or a Pasteur pipet. If you don't have access to these materials, you may want to (carefully) break a glass jar and use long, slender shards, as suggested in this tutorial, written by Alan Shinn.
Images taken through Keeling's microscope. Details here.
Don't be fooled by the simplicity of this design -- this is one powerful microscope! The quality of your images will be determined by the size and roundness of the lens, so try making a bunch of them.
[via Small Things Considered]