A microtome for in situ residence within a chamber of a scanning electron microscope (SEM) and a SEM including the microtome is disclosed. The microtome includes a specimen holder for holding a specimen thereon at high voltage to produce a retardation field thereat and a movable knife. The SEM includes a backscatter electron detector disposed adjacent to specimen holder. The knife arranged is to be carried into engagement with the specimen on the specimen holder to slice a portion of the specimen away to expose a new face of the specimen without interfering with the high voltage on the specimen, and is mounted so that after having engaged the specimen to expose a new face of the specimen it is withdrawn to a retracted position whereupon it does not interfere with the retardation field.