Gel permeation chromatography is also called as gel filtration or size exclusion chromatography. In size exclusion chromatography, the stationary phase is a porous matrix made up of compounds like cross-linked polystyrene, cross-like dextrans, polyacrylamide gels, agarose gels, etc. The separation is based on the analyte molecular sizes since the gel behaves like a molecular sieve. This technique is used for the separation of proteins, polysaccharides, enzymes, and synthetic polymers. As a technique, size exclusion chromatography was first developed in 1955 by Lathe and Ruthven. It is a technique in which the separation of components is based on the difference in molecular weight or size. The stationary phase used is a porous polymer matrix whose pores are completely filled with the solvent to be used as the mobile phase. The molecules in the sample are pumped through specialized columns containing such micro porous packing material (gel).The basis of the separation is that molecules above a certain size are totally excluded from the pores, while smaller molecules access the interior of the pores partly or wholly. The flow of the mobile phase hence will cause larger molecules to pass through the column unhindered, without penetrating the gel matrix, whereas smaller molecules will be retarded according to their penetration of the gel.