The book was called Micrographia. It provided the reading public with its first look at the world beyond the naked eye. Its author, Robert Hooke, belonged to a brilliant circle of natural philosophers who--among many other things--were the first in England to make serious use of microscopes as scientific instruments. They were great believers in looking at the natural world for themselves rather than relying on what ancient Greek scholars had claimed. Looking under a microscope at the thousands of facets on an insect's compound eye, they saw things at the nanoscale that Aristotle could not have dreamed of. A razor's edge became a mountain range. In the chambers of a piece of bark, Hooke saw the first evidence of cells.
Micrographia is is available on Google Books now.