The aim of Optical Digital Holography, applied to cells and tissue imaging, is to provide an accurate 3D imaging of biologic materials, down to the microscopic scale. The method has been developed to yield a very precise determination of cells and tissues morphology. Targeted accuracies are in the sub-micron range and allow for the observation of very small movements band deformations, produced, in particular, by depolarization of excitable cells and their metabolic activities. Direct imaging of tissue structures by the newly developed digital holography is deemed to offer unique investigation means in biology and medicine and attractive diagnostic capabilities.