Hypermedia technology needs a creative approach from the outset in the design of software to facilitate human thinking and learning. This book opens a discussion of the potential of hypermedia and related approaches to provide open exploratory learning environments. The papers in the book are based on contributions to a NATO Advanced Research Workshop held in July1990 and are grouped into six sections: - Semantic networking as cognitive tools, - Expert systems as cognitive tools, - Hypertext as cognitive tools, - Collaborative communication tools, - Microworlds: context-dependent cognitive tools, - Implementing cognitive tools. The book will be valuable for those who design, implement and evaluate learning programs and who seek to escape from rigid tactics like programmed instruction and behavioristic approaches. The book presents principles for exploratory systems that go beyond existing metaphors of instruction and provokes the reader to think in a new way about the cognitive level of human-computer interaction.