Chromatography is the science of separating mixtures into their component parts. While there are many different types of chromatography, they all have a stationary phase (does not move) and a mobile phase (moves). If each of the components of the mixture analyzed have different affinities for the mobile and stationary phases, they can be separated. The art of chromatography is selecting the correct stationary and mobile phases to use.
Two of the simplest kinds of chromatography are paper chromatography and thin layer chromatography (TLC). In paper chromatography, the stationary phase is paper and the mobile phase is a liquid solvent. The paper, with the analyte in small spots at the bottom, is put into a chamber containing the mobile phase at the bottom. Capillary action draws the mobile phase up the paper. If a component has a strong attraction for the mobile phases, it tends to move with it. If a component has a strong attraction for the paper, it tends to stay behind. The act of placing the paper into the solvent and allowing the solvent to move up the paper is called developing. The result of performing a chromatographic separation is called a chromatogram.
Thin layer chromatography is very similar except that a very thin layer of stationary phase is coated onto a glass or plastic support. The chromatogram is developed in the same way as is paper chromatography.