Tissues are processed in an automated tissue processor starting with formalin or alcohol. During this process the tissues are infiltrated with paraffin, making them firm enough to cut very thin sections.
After processing is complete, the tissues are embedded in molten paraffin inside metal molds, and then chilled. Orientation of the tissue is specified by the submitter.
The paraffin “blocks” are then mounted on a microtome, which advances the block towards a blade, each slice is 4 microns. (Thicker and thinner sections are possible – 4 microns is the standard thickness of microtomy.)
The slices of tissue and paraffin are floated on a water bath, and then placed on a glass slide. If staining is desired, we proceed with the stain the submitter requested. (The submitter can also choose unstained slides, and do their own staining.)