1. Theodor Schwann: A German physiologist who in 1839, published his observations that all animals are made of cells.
2. Matthias Schleiden: A German botanist who in 1838, observed that all plants are made of cells.
3. Rudolf Virchow: A German physician who in 1855, added the crucial third point to the theory: that all cells arise from pre-existing cells.
While these three are the most recognized, it's important to acknowledge that many other scientists contributed to the development of the Cell Theory, including Robert Hooke, who first observed cells in 1665, and Antonie van Leeuwenhoek, who observed living cells in the late 17th century.
