The purpose of fixation is to preserve the original morphological structure of cells and tissues. Fixators can prevent endogenous lysosomal enzymes from autolysis of their own tissues and cells， and inhibit the growth of bacteria and fungi. Fixing agents cause changes in the internal structure of proteins through coagulation， generation of added compounds， etc.， thereby inactivating enzymes. Fixed agents cause physical changes in the extracellular components of the nucleus. Fixed solutions are mainly divided into aldehyde fixed solutions， mercury fixed solutions， alcohol fixed solutions， oxidant fixed solutions， picrate fixed solutions， etc. The most commonly used ones are formalin in aldehydes and ethanol in alcohols.

TAF fixative， also known as trihydroxyethylamine formalin fixative， is mainly composed of formaldehyde， trihydroxyethylamine， and deionized water. This fixative is suitable for fixing nematodes. This reagent is only used in the field of scientific research and is not suitable for clinical diagnosis or other purposes.