The microscope was the greatest innovation for cell and developmental biology. Without it cells would not have been discovered. When I became a biologist, changing from engineering, I was fascinated looking down the microscope at amoebae moving and sea urchins developing. The early simple ‘microscopes’ which were really only magnifying glasses, had one lens, which could increase the size of an object nearly tenfold.
It was clearly interesting to use it to look at fleas and other tiny insects. But then came a step forward, in about the year 1590, two Dutch spectacle makers, put several lenses in a tube and made a very important discovery. The object near the end of the tube appeared to be greatly enlarged, much larger than any simple magnifying glass could achieve by itself. They had just invented the compound microscope. There was now the possibility of seeing a cell. The first person to see a cell and even give it its name was Robert Hooke in 1665 but he understood nothing.
Book suggestion: Six Impossible Things Before Breakfast - The evolutionary origins of belief (buy this book from Amazon(UK)).
Lewis Wolpert is emeritus professor of biology as applied to medicine, Department of Anatomy and Developmental Biology, University College London.