Planar-Laser-Induced Fluorescence (PLIF) is an optical diagnostic that can probe a single chemical species, such as the hydroxyl radical or the methylidine radical, in a chemically reacting flow field, providing information about the concentration, temperature, location, lifespan, and distribution of that species in the test region. PLIF is an augmentation of 1-D Laser Induced Fluorescence (LIF), which utilizes a laser source to electronically excite specific chemical species and then subsequently images the emission of those excited species. PLIF follows the same methodology as standard LIF, but adds another dimension to its measuring capabilities by including a cylindrical lens in the optical path of the laser to expand the 1-D laser beam into a 2-D laser sheet. Images of the excited species are taken perpendicular to the laser sheet. This diagnostic can be used to measure a number of characteristics of a reacting mixture, including laminar and turbulent flame thickness. Work involved PLIF in our laboratory has been in collaboration with the Kulatilaka Research Group at Texas A&M University.