Chromatography is used for the separation of a mixture of compounds into its individual components. There are several ways to accomplish this but one thing that all chromatography shares in common is the use of a mobile phase and a stationary phase. The stationary phase is motionless and is the actual medium that performs the separation. The mobile phase is what moves (usually a liquid solvent or a gas) and carries the mixture through the stationary phase. The different individual compounds in the mixture all interact with the stationary phase differently and move through it at different speeds, thus giving rise to the separation. In the classic case of the black ink being separated into its component colors using paper chromatography, the paper in this case is the stationary phase and the liquid solvent that the paper is dipped into is the mobile phase.