Who proposed that all animals are made of cells?

Theodor Schwann was a German physiologist and zoologist who, in 1839, proposed that all animals are made up of cells. Schwann studied animal tissues and noticed that they were composed of individual units, which he called "cells". 

He realized that these cells had a similar structure to the plant cells that had been described by his colleague Matthias Schleiden, and he proposed that all living organisms, both plants and animals, are made up of cells.

Hence, the correct option is Theodor Schwann.