* Robert Hooke (1665): First observed and named "cells" while looking at a thin slice of cork under a microscope. He described the small, box-like compartments he saw as "cells" because they reminded him of the small rooms monks lived in.
* Anton van Leeuwenhoek (1674): Used a more powerful microscope to observe living cells, including bacteria and protozoa. He was the first to see living cells in action.
* Matthias Schleiden (1838): Concluded that all plants are made up of cells.
* Theodor Schwann (1839): Expanded on Schleiden's work and stated that all animals are also made up of cells.
* Rudolf Virchow (1855): Added the final piece to the puzzle by stating that all cells arise from pre-existing cells.
So, while Robert Hooke made the first observations, it was the combined work of Schleiden, Schwann, and Virchow that truly established cell theory.
