In the year 1665, Robert Hooke observed a specimen of cork cells (dead) obtained from the bark of a tree under a microscope. He called them cells as they resembled tiny rooms in monasteries called cells. After Hooke’s observation, Leewenhoek was set on improving the microscope that Hooke has used for his observation. With his new and better quality microscope, Leewenhoek observed several animal cell specimens which were living and termed them as “animalcules”.