A system and method for enhancing images of ex-vivo or in-vivo tissue produced by confocal microscopy, optical coherence tomography, two-photon microscopy, or ultrasound, is provided by applying to the tissue a solution or gel having an effective concentration of citric or other alpha-hydroxy acid which enhances tissue structures, such as cellular nuclei, in such images. Such concentration may be 3-20% acid, and preferably 5% acid.