Transfer of knowledge from one context to another is one of the paramount goals of education. Educators want their students to transfer what they are learning from one topic to the next, between courses, and into the "real world." However, it is also notoriously difficult to get students to successfully transfer concepts. This issue is of particular concern in biology and the life sciences, for which transfer of concepts between disciplines is especially critical to understanding. Students not only struggle to transfer concepts like energy from chemistry to biology but also struggle to transfer concepts like chromosome structures in cell division within biology courses. This paper reviews the current research and understanding of transfer from cognitive psychology. We discuss how learner abilities, taught material, and lesson characteristics affect transfer and provide best practices for biology and life sciences education.