The first CO2 incubator developed consisted of a simple bell jar containing a lit candle. In the 1800s, researchers began searching for the ideal in vitro environment in which to maintain cell culture stocks. The appropriate quantity of atmospheric CO2 or N2 necessary for cell growth is then supplied, encouraging the microorganism to multiply, enabling easier and more definite identification. In this application, a sample is transferred to a Petri dish, placed on a rack inside the incubator and heated to body temperature (37 ☌). Laboratory incubators were first properly introduced during the second half of the twentieth century, when doctors realized that they could be used to identify pathogens from the bodily fluids of patients. Many incubators also offer features such as automatic shaking, measured by revolutions per minute. However, most modern incubators are also able to generate refrigerated temperatures, and control humidity and CO2 levels. The simplest incubators are little more than temperature-controlled ovens, capable of reaching temperatures of 60 to 65 ☌, but usually used at about 36 to 37 ☌.
Incubators are used in modern research laboratories to maintain a stable environment for processes such as growing cells and microbiological cultures and incubating antibodies and cells for fluorescence microscopy.