Composite photograph illustrating three major figures in the world of light microscopy. At bottom left is the Dutch naturalist Antoni van Leeuwenhoek (1632-1723), father of microscopy. He built his own microscopes (lower left), which he used to look further into the microworld than any of his predecessors, observing bacteria, protozoa & sperm. Right is the contribution of Robert Hooke (1635-1703) who published the first book on microscopy called Micrographia. He introduced the word 'cell' into use while observing the structure of cork. Top right is Theodor Schwann (1810-1882), German physiologist, who showed that the cell is the basic unit of life.