1. Cells The basic unit of a living organism.
Robert Hooke (~ mid 1600’s):
Looked at cork & other plants through a very simple microscope.
All cells looked like “little boxes”.
Reminded him of rooms that monks lived in, so he called them cells
He was looking at the remains of dead cells.
Anton van Leeuwenhoek (~ mid 1600’s):
Created a more powerful microscope
Studied pond water
First to view living cells.

2. Cells Matthias Schleiden (1838): Theodor Schwann (1839):
Other Important Scientists:
Matthias Schleiden (1838):
Studied plants further under a better microscope
Concluded that all plants are made of cells
Theodor Schwann (1839):
Studied animal cells further
Concluded all animals are made of cells
Rudolf Virchow (1855):
Studied living cells
Concluded that new cells are only produced from the division of existing cells

3. Cell Theory All living things are made of one or more cells.
All information collected by scientists was organized into 1 unified theory, called the Cell Theory:
All living things are made of one or more cells.
Cells are the basic units of structure and function in an organism.
Cells come only from the reproduction of existing living cells.
* Part 3 is only true now in time – not true 3.5 billion years ago!