Schematic of a CRS microscope. Two temporally synchronized lasers are used to excite the molecular vibration. For single-frequency CRS, two picosecond or femtosecond lasers can be applied. For hyperspectral CRS, a tunable picosecond laser or a femtosecond laser with linear chirping or pulse shaping is needed. A detailed description of these hyperspectral techniques can be found in the text. Abbreviations: AOM, acousto-optic modulator; CARS, coherent anti-Stokes Raman scattering; CCD, charge-coupled device; CMOS, complementary metal-oxide semiconductor; CRS, coherent Raman scattering; EOM, electro-optic modulator; fs, femtosecond pulse; G, grating; L, lens; M, mirror; PD, photodiode; PMT, photomultiplier tube; ps, picosecond pulse; SL, slit; SRS, stimulated Raman scattering.