The conversion of formaldehyde from paraformaldehyde provides fixative solutions for microscopy. When heating formaldehyde from paraformaldehyde, polymers depolymerize into active formaldehyde gas dissolved in water. This reagent preserves cellular structures for histological staining, ensuring sample stability, fine morphology, and accurate visualization of tissues under microscopes. https://www.betalifesci.com/blogs/news/how-to-make-4-paraformaldehyde-solution-in-pbs