Hooke's remarkable engineering abilities enabled him to invent and improve many mechanical devices, including timepieces (for which he invented the spiral spring), the quadrant, and the Gregorian telescope. Perhaps even more intriguing than his actual inventions are the devices he designed but never built: he anticipated the invention of the steam engine, and as early as 1684 he described a working telegraph system. At Oxford, he met Robert Boyle, who used his air pump to investigate the physical properties of gases.
Hooke balanced his inventions with more pure research. In Micrographia (1665), he coined the word cell to describe the features of plant tissue he was able to discover under the microscope. He put his extensive mathematical knowledge in formulating the theory of planetary movement, which provided a basis for Sir Isaac Newton's theories of gravitation. In 1667 he discovered the role of oxygenation in the respiratory system.
Hooke was a member of the Royal Society. After the Great Fire of 1666, he was chosen to design New Bethlehem Hospital in London, better known as Bedlam.