An optical switch enables signals to selectively switch from one circuit or fibre to another. A photonic switch also steers light, but does so within a given fibre by exploiting non-linear material properties. Nanophotonic structures are applicable to the fields of telecommunications, computation, imaging and materials engineering. The 'Single particle nanophotonic switching - bridging electron microscopy and photonics' (SPANS) project set out to investigate the processes underlying optical switching based on single-particle phase transitions triggered by light or electron-beam excitation. The EU-funded project hoped to determine the feasibility of using this principle to construct new kinds of nanophotonics switches. SPANS project partners aimed to deliver a new optical data processing concept for large-scale assembly in new photonic circuits. Efforts were also directed at the development of new techniques for the study of nanophotonic structures on the strength of combined nanophotonic and electron microscopy. Study results enabled the team to demonstrate new concepts for nanoparticle optical switch/memory and the use of electron-induced radiation emission (EIRE) for optical switching measurement. The design of new instrumentation included new forms of detectors and scanning capable of recording independent or simultaneous EIRE, electron energy loss spectroscopy (EELS) and electron energy gain spectroscopy (EEGS). SPANS successes resulted in pioneering work on EIRE and EELS mapping, as well as the development of simulation tools for EIRE, EELS and EEGS modelling. On development of the related experimental set-up, SPANS also provided theoretical proof of concept for EEGS spectroscopy.