In recent years there has been an increased interest in characterisation methods capable of evaluating the response of nanostructured materials such as quantum dots and nanotubes to externally applied stimuli. However, due to issues concerning sample homogeneity and non-uniform orientation, the study of collective responses can lead to ambiguous results. Therefore, it is crucial to perform a complementary evaluation at the single nanostructure level which requires the use of sophisticated analytical instrumentation. In addition to high spatial resolution, the equipment employed must permit sample manipulation and real-time imaging of the in situ stimulus response. Transmission electron microscopes (TEM) observe all these requirements. Furthermore, novel developments in sample holder design and manufacturing have opened a window to an unprecedented range of new in situ experiments. As a result, varied reports are increasingly populating the in situ TEM literature examining such different matters as temperature-related structural phase changes of nanoparticles or dopant diffusion in nanoscaled batteries.