This review paper examines the nature of expert performance in design, focusing on the differences between expert and novice designers. It highlights that expertise in design has distinct characteristics compared to other fields. The paper discusses the development of expertise, emphasizing the importance of deliberate practice and the accumulation of experience. It explores how expert designers differ from novices in their problem-solving strategies, particularly in their ability to decompose problems and generate solution conjectures early in the design process. The paper also delves into the cognitive processes of expert designers, such as their ability to integrate visual and technical elements, their use of parallel lines of thought, and their frequent switching between different modes of cognitive activity. Additionally, it examines the behavior of outstanding designers, noting their high standards, personal commitment, and reliance on first principles. The paper concludes by emphasizing the need for further research to establish a robust understanding of design expertise and to inform design education.This review paper examines the nature of expert performance in design, focusing on the differences between expert and novice designers. It highlights that expertise in design has distinct characteristics compared to other fields. The paper discusses the development of expertise, emphasizing the importance of deliberate practice and the accumulation of experience. It explores how expert designers differ from novices in their problem-solving strategies, particularly in their ability to decompose problems and generate solution conjectures early in the design process. The paper also delves into the cognitive processes of expert designers, such as their ability to integrate visual and technical elements, their use of parallel lines of thought, and their frequent switching between different modes of cognitive activity. Additionally, it examines the behavior of outstanding designers, noting their high standards, personal commitment, and reliance on first principles. The paper concludes by emphasizing the need for further research to establish a robust understanding of design expertise and to inform design education.