| | Re: Frozen Tissue Section Formalin Fixation
I would formalin fix first before you freeze your tissues. The whole point of the fix is to keep the morphology intact and to prevent degradation. I have heard it is generally recommended to cryo-protect your tissue samples with sucrose prior to freezing to prevent freeze artifact; however, I am not very proficient at this technique. It is also recommended to snap freeze tissues as quickly as possible to prevent freeze artifacts, especially tissues that may contain a lot of water (especially brain). You can snap freeze by liquid nitrogen or isopentane in combination with liquid nitrogen.
The absolute best reference material I recommend for histology techniques and cryosectioning is: Carson, Freida L. Histotechnology A Self-Instructional Text Third Edition. (ISBN 978-0-89189-581-7). They have an excellent troubleshooting section with each chapter and examples with sectioned tissues.