A rational approach to study cells, tissues or even organs is to isolate them from the body and bring them into a controlled, and therefore reproducible, environment. In vivo, cells are surrounded by the extracellular matrix, and the body fluids nourish them. In vitro, these fluids are replaced by culture media. In the early days of tissue culture, tissue was cultured in a drop of clotted lymph. The early-day natural nutrient media have gradually become replaced by media of a more defined composition, culminating in the advent of completely defined culture media.
Biomedical Reviews 1996; 6: 111-119.
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