Starts with 1. solvent reservoir, multiple lines for different mobile phases so the system can be isocratic or gradient. 2. Pump, decides the flow rate and the gradient. 3. Column, vary in size and packing, can be unbonded silica for normal phase or bonded silica for the more common reverse phase chromatography. 4. Detector, usually UV detector, but can be a others such as Mass Spec. detector information can be used to calculate quantity and purity as well as be used to indicate the progress of a reaction.