Agar plates

Moss growing on an agar plate.

Agar is a substance jelly-like jelly made from from red algae. It consists of agarose and a mixture of molecules known as agaropectin.

You can grow bacteria on agar plates: that is how bacteria are laid out for testing in hospital pathology departments. It is used as a place to grow bacteria in an microbiology laboratory.

Domestically, it is used to make desserts, as a laxative, and in the process of brewing.