what did schwann discover

Theodor Schwann was a German physiologist who founded modern histology by defining the cell as the basic unit of animal structure. He is best known for his discovery of the cell theory, which he extended to animals in his seminal work "Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants". Schwann also discovered an enzyme called pepsin, which is present in the human stomach and helps food digest, and he observed the formation of yeast spores and concluded that the fermentation of sugar and starch was the result of life processes.