Compact scanning electron microscope

A scanning electron microscope, comprising:

• a source of primary electrons for an electron beam;
• a lens for focusing the electron beam;
• a detector for detecting electrons from the sample;
• a removable sample holder for holding a sample for observation with the electron microscope, the walls of the sample holder forming part of the walls of a vacuum region containing the sample, and
• a sliding vacuum seal between the sample holder and the bottom of the scanning electron microscope assembly, such that vacuum pressure in the area below the lens is substantially maintained while the sample holder is removed from or provided to the vacuum region containing the sample, thereby substantially reducing the time required to evacuate the beam path to provide a vacuum adequate to form an electron microscope image of the sample.