"In vitro" is a Latin term meaning "in glass." It refers to biological experiments conducted outside of a living organism, typically in a controlled laboratory environment using test tubes, petri dishes, or other glassware. This method allows scientists to study cellular processes, drug interactions, and biochemical reactions without the complexities of a whole organism. In vitro techniques are widely used in fields like pharmacology, molecular biology, and genetics. They provide valuable insights into how cells function and respond to various stimuli, making them essential for developing new treatments and understanding diseases.