In the year of 1657 I discovered very small living creatures in rain water.
Source: In Isaac Asimov's Book of Science and Nature Quotations, by Jason Shulman & Isaac Asimov, 1988.
-- Antonie van Leeuwenhoek, (Oct 24 1632-1723), Dutch biologist; He pioneered lens-grinding and microscopy; discovered protozoa; described bacteria, 1683; studied capillary circulation.