In 1674 Anton van Leeuwenhoek peered into a drop of pond scum through a lens mounted between two metal plates (see Figure 1) and discovered an incredible world of microscopic organisms that was totally unknown to anyone at that time. In this drop of water van Leeuwenhoek observed a vast diversity of tiny “animalicule” and “cavorting beasties” that were “so exceedingly small that millions of millions might be contained in a single drop of water”.
Using an array of handcrafted microscopes that could magnify up to 300X, he went on to observe and describe protozoans such as Vorticella and Volvox, tiny animals called rotifers, spiral, grape, and rod-shaped bacteria, and parasites such as Giardia, sheep liver flukes, and trypanosomes (see Figure 2).
Since van Leeuwenhoek’s discovery of this parallel universe of microscopic organisms, an enormous amount has been learned about microbes and their profound effects on all living things.
Thousands of different types of viruses, bacteria, and parasites have been identified and their different modes of sustaining life characterized. There are doubtless more to be discovered.