Sometimes in a laboratory an urgent diagnosis is required, which can't wait for fixation of the tissue and so sections are cut fresh after the tissue is placed into a suitable cutting medium, normally OCT.

Frozen sections are cut inside a crytostat as shown in the image below.

Photo - Crytome for cutting frozen section tissue

Frozen sections, fresh smears or in most cases, both may be carried out.  For firm tissue samples, dab preparations may also be produced from tissue in that manner. It is also a requirement for Oil Red O tissue to be cut on a crytome as the fat is removed while carrying out normal Processing procedures.

Below is a picture of a frozen section Haematoxylin and eosin stain. The detail is less effective than with a paraffin processed or resin H&E, but for urgent diagnosis it can be used.

Photo - x10 Haematoxylin and eosin.