Construction of new understandings is both influenced and shaped by one’s initial (prior)—understandings, past and current experiences, perceptions or beliefs. These constitute a person’s interpretive frame and a basis upon which the individual is able to explore and understand the world around him/her. This chapter addresses the role of students' misconceptions and alternative conceptions in the learning of chemistry. Students' initial (prior) understandings are positioned and discussed as key enablers of chemistry learning and how teachers can build upon these to effect conceptual change and foster deep learning of chemistry concepts.