A major challenge in the field of optical imaging of live cells is to achieve label-free but still fully quantitative measurements, which afford high-resolution morphological and mechanical mapping at the single cell level. In particular, developing efficient, non-subjective, quantitative optical imaging technologies for cancer cell diagnosis is a challenging task. The ground-breaking goal of this research project is to establish a robust experimental toolbox for label-free optical diagnosis and monitoring of live cancer cells in-vitro and their potential of metastasis. Optical interferometry is able to provide a platform for imaging live cells quantitatively without the risk of effects caused by using external contrast agents. By overcoming critical technological barriers, I suggest novel hybrid optical interferometric approaches that provide a powerful nano-sensing tool for label-free quantitative measurement of cancer cells. This will be obtained by recording the dynamic quantitative, three-dimensional sub-nanometric structural and mechanical characterization of live cancer cells in different stages. For this aim, I will develop a novel low-noise broadband, common-path, off-axis interferometric system for sub-nanometric physical thickness and mechanical mapping of live cells in thousands of frames per second. Additionally, I will develop rapid tomographic approach for fully capturing the cell three-dimensional refractive-index distribution, as a tool to characterize cancer progression. Interferometry will be combined with multi-trap holographic optical tweezers and dielectrophoresis to enable complete cell manipulations including full rotation, imaging of non-adherent cells, and mechanical measurement validation. New set of interferometry-based quantitative parameters will be developed to enable characterization of cellular transformations, and used to characterize cancer cells with different metastasis potential, for cell lines and for circulating tumor cells.