Taken as a whole, the findings presented in the chapter provide impressive evidence that a child's knowledge base can have a great effect on memory and performance even though prior knowledge is not always used automatically. With increased accessibility of domain knowledge, both automatic and strategic processes are facilitated. Nonetheless, at all age levels, there are important differences between people in the degree of accessibility to what is stored in long-term memory. The overview given in this chapter shows that domain knowledge is a powerful determinant of memory and learning. Domain knowledge increases steadily from infancy to adulthood and contributes to the development of other sources of memory competencies, such as basic capacities, strategies, and metacognitive knowledge. Studies using the expert–novice paradigm have highlighted the importance of domain knowledge for exceptional performance in different fields such as memory, chess, music, or sports.