An ultramicrotome is a scientific instrument which is designed to prepare very thin slices of material for study under a microscope. The width of the slices varies, depending on the device and the settings chosen by the user, but can be in the tens of nanometers. To put this in perspective, this is about the size of a virus, and several orders of magnitude smaller than the width of a human hair. These instruments are sold by manufacturers and scientific supply companies, and are sometimes available for long-term leasing by labs and organizations which cannot afford the sticker price.
There are a number of different types of microscopy for which specimens prepared with an ultramicrotome can be valuable. The ability to create very thin slices can be used to explore the detailed structure of living organisms, manufactured materials, and many other substances. Microscopy techniques which these types of specimens are used for include electron microscopy and light microscopy, in which case preparing very even thin sections is important for many types of specimens.
Specimens may be prepared before they are sliced in an ultramicrotome to ensure that the slices are even and crisp. Cryosections are made by freezing a specimen before cutting, and it is also possible to force paraffin into a specimen so that it will hold its shape. When these preparations are used, a specimen sliced in an ultramicrotome will be very crisp and clean, with firm definition which will be highly visible under the microscope. One advantage to using a cryosection is that specimens can be prepared without fixative, with the properties of the specimen being kept intact.
An ultramicrotome device can be dangerous. Microtomes in general, the devices used to prepare slices for microscopy, have very sharp blades which must be handled with care. Extreme sharpness is even more critical for an ultramicrotome because the sections it prepares are so thin. It is also important to make sure that the device is well maintained to avoid problems which might be caused by miscalibration, improper lubrication, and other symptoms of neglect.
In a lab which has an ultramicrotome, people may need to schedule time on the device, reflecting the fact that numerous people want to be able to access it and that, as a result, it may not always be available. People are also usually expected to complete a course which covers safety and how to operate the ultramicrotome before they can have time alone with the device. This ensures that people are qualified to use the ultramicrotome before they start using it, reducing the risk of breakage, damage, injury, or wastes of time.