This paper presents a historical overview of visualization as a human problem-solving tool. Visualization strategies, such as mental imagery, pervade historical accounts of scientific discovery and invention. A selected number of historical examples are presented and discussed on a wide range of topics such as physics, aviation, and the science of chaos. Everyday examples are also discussed to show the value of visualization as a problem-solving tool for all people. Several counter examples are also discussed showing that visualization can sometimes lead to erroneous conclusions. Many educational implications are discussed, such as reconsidering the dominant role and value schools place on verbal, abstract thinking. These issues are also considered in light of emerging computer-based technologies such as virtual reality. (Contains 17 references.) (Author/JLB)