Principles of Cell Theory
All organisms are composed of one or more cells.
Theodor Schwann, a German botanist reached the conclusion that not only plants, but animal tissues as well is composed of cells.This ended debates that plants and animals were fundamentally different in structure. He also pulled together and organised previous statement on cells into one theory, which states: 1 - Cells are organisms and all organisms consists of one or more cells 2 - The cell is the basic unit of structure for all organisms.
Matthias Jakob Schleiden, a German botanist, proposes that all plant tissues are composed of cells, and that cells are the basic building blocks of all plants. This statement was the first generalised statement about cells.
The cell is the basic unit of structure and organization in organisms.
Robert Hooke, an English scientist, discovered a honeycomb-like structure in a cork slice using a primitive compound microscope. He only saw cell walls as this was dead tissue. He coined the term "cell" for these individual compartments he saw.
All cells come from pre-existing cells.
Rudolf Virchow, a German physiologist/physician/pathologist added the 3rd part of the cell theory. The original is Greek, and states Omnis cellula e cellula. This translates as all cells develop only from existing cells. Virchow was also the first to propose that diseased cells come from healthy cells.