Ultramicrotomy is the name given to taking thin sections off the face of a sample block. The term cryo-ultramicrotomy refers to doing this when the sample is frozen.

A glass or diamond knife is used for the sectioning. At room temperature the sections are usually floated onto a small water bath attached to the front of the knife. If cryo-sectioning is being used then the samples are cut dry and sections are lifted directly from the knife surface as they come off the block.