This technique got its name, which means "color picture", because it was first used to separate colored pigments from a single spot on a piece of paper. A solvent, such as alcohol, is allowed to move slowly across the paper, and the different components of the pigment travel at different rates.

The result is a series of separated spots of different colors. They move at different rates because of differences in the pigments' relative attraction to the paper (the "stationary phase") and their solubility in the solvent (the "mobile phase"). This principle is used in modern instrumentation to separate mixtures of organic chemicals or inorganic ions.

The components can be identified by their retention times,-- i.e., how long it takes them to pass through the instrument-- and detectors can be used to measure the amount of each component.In gas chromatography, (or, simply, "GC") the mixture of substances is injected into a narrow, coiled column, several feet long, made of an inert material like glass, silica or stainless steel. The sample has usually been extracted into an organic solvent and concentrated by evaporation as a pretreatment step.