Computer microworlds are becoming more and more powerful for learning and teaching science. However, even a powerful computer microworld is not enough, by itself, to enable students to explore and learn about a formal domain. It is argued that it should be integrated with other media, especially books. In a computer microworld, direct manipulation techniques allow the implementation of direct manipulation of physical concepts, as it is shown with an example from physics - NEWTON, a computerized exploratory laboratory. In this computerized exploratory laboratory - a conceptual laboratory - the user can explore and experiment with concrete-abstract objects, confront multiple representations and pose and devise strategies to learn about the most fundamental phenomenon of Nature: motion.