Immunoprecipitation is a laboratory technique used to isolate specific proteins from a complex mixture, such as cell lysates or tissue extracts. This method involves the use of antibodies that are specifically bound to their target protein (the one you want to study). The antigen-antibody complex is then precipitated out of solution using an agent like salt or acetone, which causes the proteins to aggregate and can be easily separated from the rest of the mixture. This technique allows researchers to selectively isolate specific proteins for further analysis such as identification, quantification, or functional studies.