A magnetic stirrer is a laboratory device used to mix liquids. It consists of a rotating magnetic field created by a magnet or an electromagnet, which drives a small magnetic stir bar placed inside the liquid. This allows for uniform mixing without the need for mechanical stirring, making it ideal for various scientific applications. These devices are commonly used in chemistry and biology labs to ensure consistent solutions and reactions. They can be adjusted for different speeds and are often used in conjunction with a heating mantle or water bath to control the temperature of the mixture while stirring.