Synchrotron nanobeams opens new opportunities to investigate nanostructures with high spatial (sub-100 nm) and temporal (sub-50 ps) resolutions. Thanks to the parallel exploitation of multiple analytical tools (fluorescence, diffraction and photoluminescence), it is demonstrated how hard X-ray nanoprobes can be currently used in nanowire research. Direct correlations of composition, structural and optical properties are obtained, providing new insights into the underlying growth mechanisms and device behavior.