Correlative video-light-electron microscopy: development, impact and perspectives

Green fluorescent protein (GFP)-based video microscopy can provide profound insight into biological processes by generating information on the 'history,' or dynamics, of the cellular structures involved in such processes in live cells. A crucial limitation of this approach, however, is that many such structures may not be resolved by light microscopy. Like more recent super-resolution techniques, correlative video-light-electron microscopy (CLEM) was developed to overcome this limitation. CLEM integrates GFP-based video microscopy and electron microscopy through a series of ancillary techniques, such as proper fixation, hybrid labeling and retracing, and so provides sufficient resolution as well as, crucially, cellular 'context' to the fluorescent dynamic structures of interest. CLEM 'multiplies' the power of video microscopy and is having an important impact in several areas cell and developmental biology. Here, we discuss potential, limitations and perspectives of correlative approaches aimed at integrating the unique insight generated by video microscopy with information from other forms of imaging.