Abstract: We compare here multi-photon excitation microscopy and tandem scanning reflected light confocal microscopy for the microscopic observation of human skin in vivo. Multi-photon excitation is induced by a 80-MHz pulse train of femtosecond laser pulses at 780 nm wavelength. This nonlinear microscopic technique is inherently suitable for tissue fluorescence imaging because of its deeper penetration depth and lower specimen photodamage. This technique has noninvasively obtained tissue structural information in human epidermis and dermis. Alternatively, tandem scanning confocal light microscopy based on a white light source can provide video-rate image acquisition with high resolution and high contrast. Reflected light confocal methods have been used to obtain images from the skin surface to the epidermal–dermal junction. The relative merits of these two techniques can be identified by comparing three-dimensionally resolved images obtained from the forearm skin of the same volunteer.