Robert Hooke

First to observe cells in 1665

Anton van Leeuwenhoek

First to observe LIVING cells

Matthias Schleiden

All plants are made up of living cells in 1838

Theodor Schwann

All animals are made up of living cells in 1839

Cell Theory

1. All organisms are composed of one or more cells, and the life processes of metabolism and hereditary occur within them 2. Cells are the smallest living thing, the basic units organization in organisms 3. Cells only arise from preexisting cells