The dominant computational cost in modeling turbulent combustion phenomena numerically with complex chemical mechanisms is associated with solving chemical kinetics. To be able to describe pollutant formation in practical fuels, the computational burden attributable to chemistry must be reduced.A presentation will be made of  the piecewise reuse approach PRISM, which divides chemical composition space into finite partitions, and in each, replaces the differential equation system of  chemical kinetics equations with a computationally simpler ”surrogate” model.   A simple introduction of Combustion will precede this, touching on: Why Combustion is studied: Some areas of practical application What goes on: Underlying physics/chemistry of flames How we study it: Experimental and computational techniques.