Cells grow in a dish. That simple statement describes a technique that underpins modern biology. Cell culture is the process of growing cells under controlled laboratory conditions. The cells may be bacteria, yeast, insect cells, or mammalian cells. They may be primary cells taken directly from tissue or immortalized cell lines that divide indefinitely. They may be grown in small flasks or in thousand-liter bioreactors.

The conditions matter. Cells need nutrients: sugars, amino acids, vitamins, and salts. They need the right temperature, usually 37 degrees Celsius for mammalian cells. They need the right pH, usually around 7.4. They need oxygen, provided through the culture medium or a gas phase. They need to be protected from contamination, which is why cell culture is done in sterile hoods with antibiotics sometimes added to the medium.

Cell culture has many uses. It produces vaccines, antibodies, and other biologics. It tests drugs for toxicity and efficacy. It studies how cells respond to signals and how diseases develop. It grows tissues for transplantation. It is a model system, a controlled environment where variables can be manipulated.

The technique is not without limitations. Cells in a dish behave differently from cells in a body. They lose their context, their neighbors, their blood supply. A drug that works in cell culture may fail in a patient. Cell culture is a starting point, not the final answer.