Label-free imaging through various optical signatures such as phase, bi-refringence and refractive index, has sensitivity down to nanometers. These techniques provide not only a complement to the fluorescence imaging at a comparable spatial resolution, but also open doors to the development of new therapeutic treatments. To date, however, capabilities for obtaining quantitative functional imaging at cellular and sub-cellular level, especially 3D data, are rather limited. This presentation will provide an overview of latest advancements in this area towards the ultimate goal of 3D nanoscopy.