Cells were discovered in 1665 by Robert Hooke, whose findings were published in the book "Micrographia." The second scientist to observe cells was Anton van Leeuwenhoek. In his work, he discovered bacteria, as well as sperm and egg cells, which disproved the theory of spontaneous generation. Hooke later confirmed van Leeuwenhoek`s findings.
One of the first people to use the newly invented microscopes extensively, Hooke began working on his observations between 1663 and 1664. His first microscopic discovery occurred while he studied a piece of cork and observed, for the first time, that it was a single unit. Though Hooke coined the word cell to describe his findings and conducted years of research, it was not until much later, in 1838, that a scientific theory noting the properties of cells was formulated.