Scanning microwave microscopy (SMM), capable of quantitatively measuring local electromagnetic properties at submicron length scales, has been widely used in semiconductor industry, materials science, physics, biology and other fields of science and technology. In particular, it offers the unique capability of penetrating into the sample-under-test in a non-invasive and non-contacting manner. However, 3D tomographic SMM systems for consistent and reproducible characterization are still not available. To address this critical need, Next 3D Tech, LLC (N3D) and the University of Maryland (UMD) propose to develop a reliable and user-friendly nonlinear scanning microwave microscopy (NLSMM) system with 3D tomographic imaging capability at the nanoscale. The main advantages of the proposed NLSMM to the state-of-the-art SMM in subsurface imaging include: better lateral and depth resolution, deeper imaging depth, more versatile platform and cost-effective. Compared to X-ray tomography, microwave tomography is especially valuable for biological applications due to the low energy level of microwave. Hence, this research and development will have great potential in biomedical applications.