What is combinatorial chemistry? Combinatorial chemistry is quickly becoming a very popular technique for organic synthesis in the pharmaceutical and biotechnology fields. Basically, combinatorial methods allow one to obtain thousands of derivatives of chemical compounds in a very quick and efficient manner. The method begins when a molecule of interest is attached to resin beads. Once the molecule is attached, a number of reactions can be run on the beads. The beads can be split up into several subsets, and different reactions can be run on each of the subsets. Because the beads are in the solid phase, it is extremely easy to separate the beads from the liquid layer after the reactions have completed.