Molecular sieve chromatography, or size exclusion chromatography (SEC) is a chromatographic technique that separates molecules in solution based on their size and, in certain situations, molecular weight. It is typically used on big compounds or macromolecular complexes, including industrial polymers and proteins. Gel-filtration chromatography is the term typically used to describe the process when an aqueous solution is used to move the sample through the column, as opposed to gel permeation chromatography, which is the term used when an organic solvent is used as a mobile phase. Fine, porous beads made of polyacrylamide (Sephacryl or BioGel P), agarose (Sepharose), or dextran polymers (Sephadex) are put into the chromatography column. Macromolecule dimensions are estimated from the pore diameters of these beads.