Which pair of scientists proposed the unified cell theory in the late 1830s?

1. By the late 1830s two researchers were studying tissues together, one a botanist and one a zoologist. 2. The botanist was Matthias Schleiden and the zoologist was Theodor Schwann. 3. Working from their tissue studies they proposed the unified cell theory. 4. Rudolf Virchow made important contributions to the theory later, so he was not one of the two who proposed it. 5. The proposing pair was Schleiden and Schwann. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 4 "Cell Structure", section 4.1 Studying Cells_