167 BCE — The Chinese use simple microscopes made of a lens and a water-filled tube to visualize the unseen.
13th century — The increase in use of lenses in eyeglasses probably led to the wide spread use of simple microscopes with limited magnification.
1590 — earliest date of a claimed Hans Martens/Zacharias Janssen invention of the compound microscope.
After 1609 — Galileo Galilei is described as being able to close focus his telescope to view small objects close up and/or looking through the wrong end in reverse to magnify small objects. A telescope used in this fashion is the same as a compound microscope but historians debate whether Galileo was magnifying small objects or viewing near by objects with his terrestrial telescope reversed.
1619 — Earliest recorded description of a compound microscope, Dutch Ambassador Willem Boreel sees one in London in the possession of Dutch inventor Cornelis Drebbel, an instrument about eighteen inches long, two inches in diameter, and supported on 3 brass dolphins.
1621 — Cornelis Drebbel presents, in London, a compound microscope with a convex objective and a convex eyepiece.
c.1622 — Drebbel presents his invention in Rome.
1624 — Galileo improves on a compound microscope he sees in Rome and presents his occhiolino to Prince Federico Cesi, founder of the Accademia dei Lincei.
1625 — Francesco Stelluti and Federico Cesi publish Apiarium, the first account of observations using a compound microscope
1625 — Giovanni Faber of Bamberg of the Linceans, after seeing Galileo's occhiolino, coins the wordmicroscope by analogy with telescope.
1655 — In an investigation by Willem Boreel, Dutch spectacle-maker Johannes Zachariassen claims his father, Zacharias Janssen, invented the compound microscope in 1590. Zachariassen's claimed dates are so early it is sometimes assumed, for the claim to be true, that his grandfather, Hans Martens, must have invented it. Findings are published by writer Pierre Borel. Discrepancies in Boreel's investigation and Zachariassen's testimony has led some historians to consider this claim dubious.
1661 - Marcello Malpighi observed capillary structures in frog lungs.
1665 — Robert Hooke publishes Micrographia, a collection of biological drawings. He coins the word cell for the structures he discovers in cork bark.
1863 — Henry Clifton Sorby develops a metallurgical microscope to observe structure of meteorites.
1860s — Ernst Abbe, a colleague of Carl Zeiss, discovers the Abbe sine condition, a breakthrough in microscope design, which until then was largely based on trial and error. The company of Carl Zeiss exploited this discovery and becomes the dominant microscope manufacturer of its era.
1967 — Erwin Wilhelm Müller adds time-of-flight spectroscopy to the field ion microscope, making the first atom probe and allowing the chemical identification of each individual atom.
1988 — Alfred Cerezo, Terence Godfrey, and George D. W. Smith applied a position-sensitive detector to the atom probe, making it able to resolve materials in 3-dimensions with near-atomic resolution.
2009 — Dame Pratibha Gai invented the in-situ atomic-resolution environmental transmission electron microscope. She decided not to patent her invention in order to further the advancement of science.