What tissue processing method makes the tissue transparent?

The tissue processing method that makes the tissue transparent is clearing. During the preparation of histological sections, clearing involves removing the dehydrating agents used in the prior steps, such as alcohol. This is achieved through the use of clearing agents like xylene or toluene, which have a refractive index that is closer to that of the embedding medium (usually paraffin). As a result, when tissues are treated with these clearing agents, the tissues become transparent, allowing light to pass through them more easily.

This transparency is essential for the subsequent embedding step, as it facilitates the penetration of the embedding medium into the tissue, ensuring that the sections can be cut with precision during microtomy. The clear tissue also allows for improved visualization and analysis of cellular structures when the tissue is finally stained and examined under a microscope, ultimately enhancing diagnostic accuracy.