Taken together, these results demonstrate that characteristic U VI O2 2+ emission can be used in 2PE microscopy to directly study uranium distribution and molecular environment in cellular systems, without the need for additional dyes. While U VI O2 2+ species show very low two-photon cross sections, comparable to that of common biological fluorophores, the long-lived U VI O2 2+ emission is readily observed by PLIM. The ability to map aggregates of biomass and uranyl-containing materials while simultaneously probing the coordination environment of the metal using lifetime imaging has been applied to the biosorption of U VI O2 2+ by yeast to demonstrate that carbonate does not appear to inhibit binding. This stands in contrast to the sorption of U VI O2 2+ on clay minerals and suggests that further work needs to be applied to study biosorption in solutions that better emulate groundwater, potentially in concert with other speciation-sensitive techniques such as Raman mapping. While most bacteria are an order of magnitude smaller than the fungal cells used for biosorption the high resolution obtained from two-photon microscopy has shown it to be a potentially useful technique for studying the enzymatic reduction of U VI to U IV by dissimilatory bacteria such as Geobacter sulfurreducens.