A lab technique; a type of column chromatography, used to separate the components of a mixture by molecular size and to collect the molecules which are larger than a certain size. It is similar to gel filtration; small molecules are slowed or trapped by the pores in the gel beads filling the column, while large molecules, too large to fit into the pores, slide past the beads and get to the bottom of the column first. At this point, the large molecules are collected."Gel exclusion" refers to the maximum size of molecule which will fit into the gel bead pores, and this lab technique is used to collect the molecules in the mixture which are larger than, or "excluded" from, the pores.