Abstract: Flow and mass transport processes in Angstrom-scale confined spaces have emerged as a forefront area of study in fluid mechanics. As the critical size of a channel decreases to sub-nanometer or approaches the molecular scale, the transport behaviors deviate from those observed in macroscopic fluids, where the continuum assumption may no longer apply. A significant problem is the absence of experimental characterization of flows and transport phenomena at such small sizes. This paper summarizes the principal experimental methodologies for investigating fluxes and transport within confinement. We categorize the experimental methods into four distinct types: weight-change measurements, optical imaging, electrical measurements, and spectroscopies. We succinctly present the foundational principles and examine the merits and limitations of each experimental approach. Our work serves as a reference for the subsequent advancement of measuring procedures for transport in extremely confined spaces.