Tu, H. et al. Nat. Photonics 10, 534–540 (2016).

Histopathology is widely used both in the laboratory and in the clinic. Although powerful conventional methods exist for fixing and staining tissues for imaging, they are time-consuming and can introduce artifacts. Label-free imaging methods such as multiphoton microscopy can overcome some of these issues, as they can be used to image fresh, unstained tissues. Tu et al. introduce a user-friendly approach for label-free histopathology that allows for fresh tissues to be imaged with a combination of two-photon autofluorescence, three-photon autofluorescence, second-harmonic generation, third-harmonic generation and coherent anti-Stokes Raman scattering or stimulated Raman scattering. This combination is enabled by a light-delivery system that could easily be programmed for optimal contrast in the different imaging modalities, and it was used to visualize microstructures in tissues that are not easily seen with conventional methods.