Robert Hooke's Micrographia opened up a whole new world of previously unseen wonders. Historian of Science, Felicity Henderson, discusses the fascinating book and how it completely amazed Samuel Pepys.

While visiting his bookseller on a frosty day in early January 1665 Pepys noticed a copy of Robert Hooke's Micrographia, 'which', Pepys recorded in his diary, 'is so pretty that I presently bespoke it'. Like many other readers after him, Pepys was immediately drawn in by the beautiful engravings printed in Micrographia, the world's first fully-illustrated book of microscopy. When he picked up his own copy later in the month Pepys was even more pleased with the book, calling it 'a most excellent piece . . . of which I am very proud'. The following night he sat up until two o'clock at night reading it, and voted it 'the most ingenious book that ever I read in my life'.
Drawing of Robert Hooke's microscope from Micrographia
An example of the microscope Hooke used is in the exhibition
Thus Pepys was one of the first people to explore the strange new world of microscopic objects described by Hooke. Micrographia was the result of several years of microscopical research, much of which Hooke had presented at meetings of the Royal Society. Observations of insects and plant material were interspersed with everyday items such as woven cloth, feathers, hair, sand, and the fiery sparks that leapt from a flint struck with steel. In the accompanying text Hooke suggested how the microscopic structures of the natural world might determine the properties of materials and enable insect bodies to carry out specific tasks. For example, his discovery that cork is made of tiny individual 'cells' seemed to explain cork's buoyancy and why it contracts under pressure: Hooke thought each cell might contain air which could be slightly compressed by external force. 
Hooke's drawing of  Cork cells in Micrographia
Hooke was the first to apply the word "cell" to biological objects
But Micrographia was much more than a scientific textbook. As one of the earliest publications sponsored by London's new scientific institution, the Royal Society, Micrographia attempted a much bolder task - to persuade readers to see the world differently. The first illustration depicts the point of a needle, the edge of a razor, and a printed full-stop. Seen through Hooke's microscope, these seemingly fine, sharp objects are blunt, pitted and jagged. Man-made artefacts are rude, mis-shapen things which can't compete with the beauty and precision of the natural world. The book's eye-catching illustrations reinforce this point, going far beyond what would be required for a scientific explanation, startling readers with 'a flea the size of a cat', as one contemporary commented to a friend.
Drawing of a flea from Micrographia by Robert Hooke
Drawing of a flea from Micrographia by Robert Hooke, 1665
Pepys may have been impressed by Micrographia because he himself owned a microscope – ‘a most curious bauble’ that had cost him £5 10 shillings, ‘a great price’. He and his wife had made their own laborious observations ‘with great pleasure, but with great difficulty’. Perhaps because of this, Pepys retained a profound respect for Robert Hooke. Just three weeks after first reading Micrographia he became a Fellow of the Royal Society, and attended a post-meeting supper where above all the other gentlemen-philosophers present he ranked 'Mr. Hooke, who is the most, and promises the least, of any man in the world that ever I saw'.

To see Micrographia and discover more about Samuel Pepys's role as President of the Royal Society visit Samuel Pepys: Plague, Fire, Revolution