Aton Van Leeuwenhoek was the first scientist to discover prokaryotic organisms. These single-celled organisms lack a nucleus and other membrane bound organelles but do have a cell membrane, DNA, and even a cell wall. Choice one of the answer. A. All known living things are made up of one or more cells. B. All living cells come from pre-existing cells by division. C. A cell is the fundamental unit of structure and function in all living organisms. D. No answer text provided