Isotonic saline is a sterile solution of sodium chloride (salt) in water, typically containing 0.9% salt. It is called "isotonic" because its salt concentration is similar to that of the body's cells, which helps maintain fluid balance. This solution is commonly used in medical settings for various purposes, including hydration, wound cleaning, and as a diluent for medications. In addition to its medical uses, isotonic saline is often employed in laboratory settings for cell culture and other scientific experiments. It is important for maintaining the proper osmotic pressure, ensuring that cells do not swell or shrink when exposed to the solution.