Semiconductor nanowires offer new opportunities for optoelectronic and spintronic nanodevices. However, their full potential is ultimately dictated by our ability to control multiple property‐function relationships taking place at the nanoscale in the spatial and time domains. Only a combination of high‐resolution analytical techniques can provide a comprehensive understanding of their complex functionalities. Here we describe how a multimodal hard X‐ray nanoprobe addresses fundamental questions in nanowire research. Selected topics ranging from cluster formation, dopant segregation, and phase separations to quantum confinement effects are investigated with sub‐100 nm spatial resolution and sub‐50 ps temporal resolution. This approach opens new avenues for structural, composition and optical studies with broad applicability in materials science.