Physiologist Theodor Schwann and botanist Matthias Jakob…

Physiologist Theodor Schwann and botanist Matthias Jakob Schleiden develop cellular biology in 1839.

Cells were first seen in seventeenth century Europe with the invention of the compound microscope

In 1665, Robert Hooke termed the building block of all living organisms as "cells" after looking at a piece of cork and observing a cell-like structure; however, the cells were dead and gave no indication to the actual overall components of a cell.

A few years later, in 1674, Anton Van Leeuwenhoek was the first to analyze live cells in his examination of algae.

All of this preceded the cell theory which states that all living things are made up of cells and that cells are the functional and structural unit of organisms.

This is ultimately concluded by Schleiden and Schwann, who view live cells in plant and animal tissue, respectively.