Biological fluids are liquids found within living organisms that play key roles in maintaining biological functions. These fluids include blood, lymph, saliva, sweat, urine, cerebrospinal fluid, and various digestive juices. They carry essential nutrients, hormones, and waste products throughout the body, regulate body temperature, and protect the body from infections. Research in the field of biological fluids focuses on understanding the composition, properties, and functions of these fluids, as well as their potential diagnostic and therapeutic applications in health and disease. This research area often involves the study of biomarkers, proteins, metabolites, and other molecules present in biological fluids to identify indicators of various health conditions, predict disease progression, and develop new treatments and diagnostic tools.