An isotonic solution is a type of solution that has the same concentration of solutes as another solution, typically a cell's internal environment. This balance allows for the equal movement of water in and out of the cell, preventing any net gain or loss of water. Common examples of isotonic solutions include 0.9% saline and lactated Ringer's solution, which are often used in medical settings. In biological contexts, isotonic solutions are crucial for maintaining cell health. When cells are placed in an isotonic solution, they retain their shape and function properly. This is important for processes such as osmosis, where water moves across cell membranes, ensuring that cells do not swell or shrink excessively.