Tacit knowledge, that is knowledge not expressible in words, may play a role in learning science, yet it is difficult to study directly. Intuition and insight, two processes that link the tacit and the explicit, are proposed as a route to investigating tacit knowledge. Intuitions are defined as tacit hunches or feelings that influence thought with little conscious effort. This paper examines conceptualisations of intuition as embodied cognition, and as abstracted rules before examining reports of intuition in the work of scientists and in science education. Insight is described as an explicit awareness of novel relations between concepts that arrives with little conscious control. Insight is related to rapid conceptual change and the development of conceptual connections. Reports of insight in the work of scientists and in the science classroom are discussed. The manner in which insight and intuition may promote and hinder learning is considered and conditions that affect the use of both processes are suggested. Strategies that might encourage students' use of intuition and insight in the classroom are proposed. The paper concludes with a call for a greater focus on the concept of tacit knowledge in science education and suggests areas for future research.