MÜLLER stock solution, a combination of potassium dichromate and sodium sulfate in water, is mainly used in histology and medical diagnostics. It enables the fixation of tissue samples by preserving the natural structure of proteins and other biological materials. As a strong oxidizing agent, potassium dichromate reacts with organic substances, while sodium sulfate serves as a stabilizer and prevents undesirable side reactions. The solution's mode of action is based on potassium dichromate's ability to break covalent bonds in organic molecules and convert them to a more stable, fixed form. The use of this solution enables the generation of high-resolution histological preparations and the performance of accurate diagnostic tests. It should be noted that changes in color or consistency during application may indicate chemical reactions with the biological material. MÜLLER's stock solution thus represents an important tool for scientific and medical investigations.