The cell was first discovered by Robert Hooke, an English scientist, in 1665. He observed tiny box-like structures in a thin slice of cork under a self- designed microscope and called them "cells" because the compartments reminded him of the small rooms, or "cells," that monks lived in. Hooke described these observations in his book "Micrographia." However, what Hooke observed were actually the cell walls of dead plant tissue, and he did not see the internal structures like the nucleus or organelles. Shortly after Hooke, Antonie van Leeuwenhoek, a Dutch scientist, improved the microscope and was the first to observe live single-celled organisms and bacteria, which he called "animalcules." His work significantly contributed to the establishment of cell theory. In summary, Robert Hooke discovered and named the cell in 1665 by observing cork under a microscope, and Anton van Leeuwenhoek furthered the understanding of living cells by observing microorganisms with his improved microscopes.