Which scientist proposed that all animals are made of cells?

The belief that all animals are made of cells is credited to Theodor Schwann, a pivotal figure in the development of cell theory. In the 1830s, Schwann, alongside Matthias Schleiden, contributed significantly to the understanding that both plants and animals are composed of cells, marking a key advancement in biological science. Schwann's work emphasized the idea that the cell is the fundamental unit of life in animals, reflecting the principles of cell theory that state all living organisms are made of cells, and that cells are the basic unit of structure and function in organisms.

This contribution established a foundational concept in biology, underlining the significance of cellular composition in understanding the organization of living beings. The development of this concept helped form the basis for much of modern biology and underscores the importance of the cell in both the structure and function of living organisms.