Because most viruses are too small to be observed by light microscopy, electron microscopy (EM) is the method of choice for the direct visualization of viruses and viral proteins. To survive the high vacuum inside the microscope, biological samples have to be dehydrated and/or fixed. We describe the different kinds of single particle preparations such as negative staining, cryo-EM and metal shadowing as well as several sectioning techniques including CEMOVIS. We also mention image analysis, 3D-reconstruction and combination of the obtained EM data with data from other structural biology techniques. Images of adenovirus particles, adenovirus proteins and adenovirus-infected cells are used as illustrations.