Agarose gel is used for DNA separation. This gel has been found to be most effective for separating DNA fragments between100 bp and 25 kb.

Agarose gel is essentially a polysaccharide. It comes as dry, powdered flakes. When heated in a buffer composed of water containing some salts and then allowed to cool, it forms a gel that is solid but slightly squishy. 

At the molecular level, agarose gel is composed of a matrix of agarose molecules held together by hydrogen bonds. Wells, which are pocket-like indentations, form at one end of the gel. DNA samples are placed in these wells.