Firefly Luciferase, also known as Photinus pyralis luciferase (FLuc), is a widely used enzyme in bioluminescence imaging due to its well-characterized properties and high sensitivity in detecting light output. The enzyme catalyzes the oxidation of luciferin in the presence of oxygen, ATP, and Mg2+ to produce a yellow-green light with a peak emission at 560-578 nm. This bioluminescent reaction is highly efficient and does not require any additional substrates or cofactors, making it an ideal reporter for gene expression studies and imaging in living organisms.