A long-held and central objective of science instruction is to help students develop scientific reasoning patterns. During the past few decades, considerable research has been undertaken to identify the nature of scientific reasoning patterns, their “natural” paths of development, and there role in concept acquisition, as well as how science instruction can help in their development. This chapter describes the nature of scientific reasoning and argumentation and it includes instructional strategies to help college students develop advanced scientific reasoning patterns and construct key biological concepts and theories.