Fixatives are chemicals that act as preservatives or stabilizing agents. They perform various functions and are used extensively in the fields of histology, cell biology, and pathology.

Fixatives perform these important functions: 

• Prevent autolysis and putrefaction, which helps to preserve cells, tissues and subcellular substances as close as possible to their original living state
• Render cell components insoluble, thus protecting them from changes by subsequent treatments 
• Harden tissues, making gross cutting easier 
• Protect tissues from osmotic damage, which helps tissues retain their original size and shape during processing
• Make tissue more permeable for subsequent reagents   
• Facilitate clear staining of sections 
• Emphasize the differences in refractive index, which improves optical differentiation of cells and tissues