Many chromatographic techniques are performed in “columns." These are tubes containing the material (called the “support") used to perform the separation . Supports are designed to exploit the chemical, or size, differences of the many molecules in a mixture. Columns are “packed" (filled) with the support and a buffer or solvent carries the mixture of compounds to be separated through the support. Molecules in the sample interact differentially with the support and consequently, will travel through it with different speeds.