Fluid flow and transport through porous materials is ubiquitous in nature and engineering. The pores of rocks in the subsurface hold groundwater reserves and can store hydrogen and carbon dioxide. Over the past years, micro-CT has become an indispensable tool to study fluid flows in these porous media, thanks to its ability to visualize pore structures and what goes on in them. In this talk, I will discuss our latest progress on using this to improve our understanding of such flows from the pore- to the core-scale. First, I will show it is now possible to measure 3D flow fields with micrometer-scale resolutions in rock samples.