Agar agar

Agar or agar agar is a gelatinous substance derived from seaweed. Historically and in a modern context, it is chiefly used as an ingredient in desserts throughout Japan, but in the past century has found extensive use as a solid substrate to contain culture medium for microbiological work. The gelling agent is an unbranched polysaccharide obtained from the cell walls of some species of red algae, primarily from the genera Gelidium and Gracilaria, or seaweed Sphaerococcus euchema. Commercially it is derived primarily from Gelidium amansii.
Agar can be substituted for gelatine but has stronger setting properties, about 5 times greater so less of it is required. Unlike gelatine, agar will set at room temperature. It comes in variety of substances. Some can be bought in sheets or alternatively you can buy the powder.