The structure of biological material (e.g. cells) is crucial for understanding the way in which they function/interact with their environment. In the SEM secondary electron imaging can provide important information on the shape at length scales varying from micrometers down to several nanometres. TEM provides higher spatial resolution, but the low contrast of biological material is often a problem. Techniques such as energy filtering can help improve the contrast, especially if the material is thick. Furthermore electron tomography can be used to reconstruct the 3D shape at nanometre spatial resolution, by acquiring a series of images of the specimen at different tilts.