Final answer:
Robert Hooke is credited with discovering cells in cork, which contributed to the development of the cell theory.
Step-by-step explanation:
In 1665, the English physicist Robert Hooke used a microscope to examine a piece of cork and discovered tiny structures that he called cells. He published his observations in his book Micrographia and described these structures as resembling honeycombs or small chambers. Hooke's discovery of cells was a significant contribution to the field of biology and eventually led to the development of the cell theory, which states that all living organisms are made up of cells.