Non-Newtonian fluids are widely used in a variety of research areas as well as numerous industrial applications, including the food, pharmaceutical, and petroleum industries. As rheologists, the internal structures of these complex fluids are of significant interest as it allows us to analyze and understand better the obtained results of rheological experiments. To understand the industrial processes, there are several model fluids that are used to study and optimize these processes. Moreover, it is important to understand how these fluids respond when their composition changes due to the addition of nanoparticles, so that their rheological behavior can be improved. In this sense, the visualization of the fluid microstucture and how it relates to rheology can provide important information. Cryo-Scanning Electron Microscopy (cryo-SEM) is a one reasonable means for observing and investigating the microstructure of complex fluids. Using this method, we show the microstructure of some fluids and nanofluids, and relate these microstructures to the rheology and to flow behavior. We present some promising implementation cases of this cryo-SEM approach for various non-Newtonian fluids.