Fluorescence Spectrophotometers measure the light a sample emits after absorbing light at a shorter wavelength, detecting many compounds at far lower concentrations than absorbance methods. Dual monochromators select excitation and emission independently across 200 to 900 nm, with slit widths of 1 to 20 nm to trade sensitivity against resolution. Wavelength accuracy holds within 0.1 to 1 nm and repeatability within 0.2 to 0.5 nm, while signal to noise reaches 150:1 on the water Raman peak and up to 1000:1 RMS on high-end models. Typical uses include DNA and protein quantification, enzyme kinetics, biomarker assays, drug formulation QC, pollutant screening and quantum dot research.