The first contribution made to the cell theory was by a scientist named Robert Hooke. In 1665, Hooke was the first to discover cells. Hooke made this discovery by cutting thin slices of a cork and examining them under a microscope. Hooke found that inside this cork contained a multitude of tiny pores that reminded him of the walls of a honeycomb. Hooke called these pores cells and published his findings in Micrographia, the first book to illustrate plants, insects, and more through a microscope.