Hans Spemann's Experiment was a groundbreaking study in developmental biology conducted in the early 20th century. Spemann used embryos of newts to investigate how cells differentiate during development. He discovered that certain cells could influence the fate of neighboring cells, leading to the formation of specific tissues and organs. In his experiment, Spemann employed a technique called "organizer transplantation." He removed a small section of the embryo, known as the organizer, and transplanted it to another part of the embryo. This manipulation demonstrated that the organizer could induce the development of a complete secondary body axis, highlighting the importance of cell signaling in embryonic development.