Agar is an excellent solidifying agent due to its stability at higher temperatures. In microbiology, agar is useful as a growth medium for organisms that grow under high temperature, and it can also be used for organisms that thrive under lower temperatures, such as fungi.
Very few microorganisms can subsist off agar, further increasing its utility. In comparison, substrates such as gelatin are commonly used by microorganisms as food, reducing their effectiveness. Rhodophyta algae are used in the production of agar. When boiled, their cell walls release polysaccharide agarose, the chemical that forms agar when mixed with agaropectin. Agar is usually available in powder form and is mixed with water and nutrients to create an ideal surface for microbial study.
In cooking, agar is a vegetable substitute for gelatin, where it can be used to make puddings, jellies and custards. The high fiber content of agar allows it to function as a regularity aid. When swallowed, agar absorbs a significant amount of water, meaning that it can be used as a dietary supplement as well. Agar's other uses include modeling clay, dental impressions, ant farms and salt bridges. It was discovered in Japan around 1658 by Minoya Tarozaemon, who discarded seaweed soup and found it congealed the next morning due to the extreme cold of the previous night.