The high spatial resolution (approximately 350 nm) transmission digital microscopy (TDM) was developed for real time in vivo imaging of microlymphatics of rat mesentery at a single cell level without any contrast agent. The main mesenteric microstructures (lymph-vessel diameter, valve geometry, cells, etc.) and their dynamics (wall motion, valve function, cell velocity, etc.) were monitored with TDM. Depending on structure size, different magnifications were used to image relatively large whole lymphangion (x4 to x10) as well as to image single cells (x40 to x100) in lymph and blood flow including estimation of their shape, size, and aggregation state. Various potential applications of the TDM for in vivo studies are discussed, including visualization of circulating cells in lymph and blood flows, studying the kinetics of platelets, leukocyte rolling, as well as imaging absorbing nonfluorescent mesentery structures and leukocytes with a high optical resolution.