1. Discovery of the Cell

2. The Cell Theory
…also, by the early part of the 19th century enough biological material had been observed to begin to make generalizations.

3. Matthias Jakob Schleiden
A botanist and microscopist
In 1838 declared that the plant organism is made of cells
He accepted the importance of the nucleus, discovered by Robert Brown ( ), and speculated on its role in cell division
, Germany

4. Theodor Schwann He was a zoologist and a microscopist
Physiologist and microanatomist
Discovered the connection between yeast and fermentation
Following Schleiden’s pronouncement, declared that animals, too, are made of cells as the fundamental building blocks
, Germany

5. Virchow and Remak
Virchow’s cell theory
Rudolph Carl Virchow ( , Germany) suggested that disease is a cellular problem
He stated that all cells come from pre-existing cells, a theory stated earlier by Robert Remak ( , Poland)
Virchow ( )
Remak ( )

6. The Cell Theory by 1858
All living organisms are composed of one or more cells.
The cell is the most basic unit of structure, function, and organization in all organisms.
All cells come from pre-existing, living cells.

7. Histology and Paul Ehrlich
Aniline dyes had been derived from coal tars in the early part of 19th Century
Karl Weigert ( , Germany) used an aniline dye to stain bacteria
Ehrlich experimented with staining human tissues
He used chemical treatments to serve as the first chemotherapy (used Methylene Blue for syphilis)
, Germany
The use of aniline dye to stain white blood cells

8. Development of Optical Staining
Bright field
Polarized light
Darkfield
Phase-Contrast
Differential Interference
Contrast
Fluorescence Imaging

9. The Cell Cycle: Mitosis

10. Reduction Division: Meiosis
First described by Oskar Hertwig ( , Germany) in 1876 in the formation of sea urchin eggs.
Described again by Edouard van Beneden ( , Belgium) in 1890 in the formation of Ascaris eggs.
August Weismann ( , Germany) noted in 1911 that the reduction of chromosome numbers, employing meiosis, was necessary if nuclei were to fuse in sexual reproduction

11. Meiosis

12. Electron Microscopy
Two types: Transmission (TEM) and Scanning (SEM)

13. Transmission Electron Microscopy
Leo Szilard (1928) filed patent for electron microscope in concept
The prototype built in 1931 by Ruska and Knoll
Resolution limit for light microscope ~2,000X; but the limit for TEM ~2 millionX
Max Knoll ( , Germany, left) and Ernst Ruska( , Germany, right) with first TEM

14. Scanning Electron Microscopy
Vladimir Kosmich Zworykin ( , Russia and USA) invented SEM and television (both based on raster principle)
With early television (kinetoscope) in 1929

15. Details of Subcellular Structures with EM
Membranes

16. Details of Subcellular Structures with EM
Nucleus

17. Molecular details of the nuclear envelope by Mahamid et al. (2016)
A new method for visualizing molecular cellular components using TEM

18. Details of Subcellular Structures with EM
Chloroplast

19. Details of Subcellular Structures with EM
Mitochondria

20. Details of Subcellular Structures with EM
Endoplasmic Reticulum

21. Details of Subcellular Structures with EM
Flagellum or Cilium

22. Current View of the Cell Theory
All known living things are made up of one or more cells.
All living cells arise from pre-existing cells by division.
The cell is the fundamental unit of structure and function in all living organisms.
The activity of an organism depends on the total activity of independent cells.
Energy flow occurs within cells.
Cells contain hereditary information (DNA) which is passed from cell to cell during cell division.
All cells are basically the same in chemical composition in organisms of similar species.