Fixation and Sectioning

Most biological tissue samples are thick and opaque and must be processed before being observed under a microscope.

The tissues are first treated using a fixing solution that kills the cells and immobilizes the cellular components to maintain their structure.

The fixed samples are passed through an increasing gradient of alcohol, which dehydrates the sample.

To prevent the fragile samples from being damaged, they are embedded in a water-repelling material like paraffin wax and sliced into thin sections with a microtome.

The thin sections are transferred to slides, where a few drops of organic solvents are added to remove the adhering wax.

Next, the sections are stained, and a mounting medium is added, with a coverslip on top. The mounting medium should have the same refractive index as the coverslip and the slide to obtain the best image resolution.

The sample is now ready for visualization under a microscope.