Final answer:
Robert Hooke coined the term "cells" in 1665 to describe the compartments he saw in cork when viewed under a microscope, which were crucial for cell theory development.
Step-by-step explanation:
The English scientist Robert Hooke first used the term "cells" in 1665 when describing the tiny compartments he observed in a slice of cork under his microscope. Hooke used the term because these compartments reminded him of the cells inhabited by monks, small rooms in a monastery. He published his observations in Micrographia, and these findings were crucial for the later development of cell theory. Cork itself is a natural material obtained from the bark of cork oak trees. When Hooke observed cork under the microscope, he saw what resembled a honeycomb structure, but what he did not realize at the time was that the cork cells were no longer alive and lacked the internal structures typical of living cells.