Research Techniques Made Simple: Two-Photon Intravital Imaging of the Skin.

Over the last few years, intravital two-photon microscopy has matured into a powerful technology helping basic and clinical researchers obtain quantifiable details of complex biological mechanisms in live and intact tissues. Two-photon microscopy provides high spatial and temporal resolution in vivo with little phototoxicity that is unattainable by other optical tools like confocal microscopy. Using ultrashort laser pulses, two-photon microscopy allows the visualization of molecules, cells, and extracellular structures up to depths of 1 mm within tissues. Consequently, real-time imaging of the individual skin layers under both physiological and pathological conditions has revolutionized our understanding of cutaneous homeostasis, immunity, and tumor biology. This review provides an overview to two-photon microscopy of the skin by covering the basic concepts and current applications in diverse preclinical and clinical settings.