Fig. 3
From: Intravital microscopy imaging of kidney injury and regeneration
Principle and schematic setup of intravital two-photon microscopy. a Scheme for one-and two photon excitations. Unlike single photon excitation, which uses a continuous photon flux, two-photon effect is a phenomenon in which a molecule “almost” simultaneously absorbs two photons of the same or different frequencies, causing the molecule to transition from a low-level to a high-energy state, which is a nonlinear optical effect. b Schematic of the intravital two-photon system using AIW