science - Timeline

Jenson credited with 1st compound microscope

Hooke described 'cells' in cork

Leeuwenhoek discovered protozoa. He saw bacteria some 9 years later.

Brown descibed the cell nucleus in cells of the orchid.

Schleiden and Schwann proposed cell theory.

Albrecht von Roelliker realized that sperm cells and egg cells are also cells.

N. Pringsheim observed how a sperm cell penetrated an egg cell.

Rudolf Virchow (physician, pathologist and anthropologist) expounds his famous conclusion: omnis cellula e cellula, that is cells develop only from existing cells [cells come from preexisting cells]

Kolliker described mitochondria.

Flemming described chromosome behavior during mitosis.

Germ cells are haploid, chromosome theory of heredity.

Golgi described the golgi apparatus.

Behrens used differential centrifugation to separate nuclei from cytoplasm.

Siemens produced the first commercial transmission electron microscope.

Gey and coworkers established a continuous human cell line.

Eagle systematically defined the nutritional needs of animal cells in culture.

Meselson, Stahl and Vinograd developed density gradient centrifugation in cesium chloride solutions for separating nucleic acids.

Ham introduced a defined serum-free medium. Cambridge Instruments produced the first commercial scanning electron microscope.

Sato and colleagues publish papers showing that different cell lines require different mixtures of hormones and growth factors in serum-free media.

Transgenic mice and fruit flies are produced. Mouse embryonic stem cell line established.

Tsien identifies mutant of GFP with enhanced spectral properties

Hamilton and Baulcombe discover siRNA as part of post-transcriptional gene silencing (PTGS) in plants