Tissue swelling may occur.o Prolonged fixation: Shrinkage of the tissue causes tissue separation and empty spaces.Fixation Artefact: Formalin pigment: Insoluble brownish-black granular retractile birefringent pigment due to reaction of formalin with hemoglobin derivatives.o Mechanism of formation: Formic acid reacts with hemoglobin derivatives of the blood and produces acid formaldehyde haematein.It provided firmer texture to the tissues and gives brilliance to the staining.o Fuzzy staining: Due to improper fixation.5.6.???