This document outlines the timeline and development of the Cell Theory. It began in the late 1500s with the invention of the compound microscope, allowing Hooke to observe "cells" in plant tissues in 1665. Later discoveries included Leeuwenhoek viewing single-celled organisms in pond water in 1673. In 1838, Schleiden concluded that plants are made of cells after examining plant tissues microscopically. In 1839, Schwann made the same conclusion about animals being made of cells. Finally, in 1855 Virchow studied cell reproduction and stated that new cells come from existing cells, contributing to the full Cell Theory that all living things are made of cells, cells are the basic functional unit, and new

1. The Cell Theory – a timeline Late 1500’s: -first lenses used in Europe -used to determine cloth quality (weave and precision) -combos of lenses gave better view -Hans Janssen and son Zacharias invented first compound microscope in 1590

3. Looked empty, like monk’s chamber

5. first to view pond water organisms

6. First to see living microscopic orgs

8. All plants looked at were made of cells, so concluded:“All plants are made of cells.”

10. Saw that all animals he studied were cellular so concluded:“All animals are made of cells.”

13. Cells are the basic units of structure and function in living things

14. New cells are produced from existing cells