The word surfactant is a contraction of surface active agent. Surfactants have also been called stabilizers, cell control additives, foam stabilizers, and cell control agents, among other titles. Surfactants impart stability to the urethane polymer during the foaming process. They help control cell structure by regulating the size and, to a large degree, the uniformity of the cells. The choice of surfactant is governed by factors such as polyol type and method of foam preparation. Structural parameters of silicone surfactants such as the ratios of ethylene oxide (EO)/(EO + PO), and (EO + PO)/Si are major factors of silicone surfactants. The co-use of silicone surfactants and catalysts made possible production of urethane foams. Silicone surfactants are used to stabilize the foaming reaction, to act as an emulsifier for certain compounds, and to assist in mixing.