In Vivo Methods refer to experimental techniques conducted within a living organism. These methods are essential for studying biological processes in their natural context, allowing researchers to observe how systems function in real-time. Common applications include drug testing, disease modeling, and understanding physiological responses. These methods can involve various organisms, from simple model organisms like fruit flies to complex mammals such as mice or even humans. By using in vivo approaches, scientists can gather data that reflects the intricate interactions of cells, tissues, and organs, providing insights that are often unattainable through in vitro studies.