We are beginning to investigate high resolution ultrasound elasticity imaging methods to enable noninvasive visualization of structures smaller than 1 mm3 based upon contrast in mechanical stiffness. Increases in tissue stiffness can arise through deposition of collagen, inflammatory responses, and the increased nuclear density associated with malignancy. Some potential applications for this technology include tumor margin characterization, lymph node assessment, quantification of atherosclerotic plaque composition, and tumor micro-environment characterization. A high resolution (i.e. sub-mm) micro-elasticity imaging system will enable earlier and more detailed visualization of pathologic and malignant processes, leading to better informed diagnostic, prognostic, and therapeutic clinical decisions. Below is an example of our initial in vivo visualization of axillary lymph node anatomical structures using B-mode and ARFI.