Pathology is the study of disease and the associated changes that occur at the cellular, tissue, and organ levels. This leads to signs and symptoms in patients. Pathology examines the causes, structural changes, and symptoms of diseases. Techniques used in pathology include microscopic examination of tissues and organs, histochemistry using special stains, immunohistochemistry to visualize proteins, electron microscopy to study subcellular structures, and biochemical and molecular analysis. The overall aim is to diagnose diseases, determine treatment and prognosis, and contribute to medical research.