This book presents a comprehensive overview of computation performed by physical, chemical, biological, and quantum systems, bringing together leading international researchers working at the intersection of computer science, physics, chemistry, materials science, biology, and engineering. As conventional silicon technologies approach their physical and energetic limits, unconventional computing is emerging as one of the most exciting frontiers of modern science. The chapters explore a remarkable diversity of computational substrates, including DNA, gene regulatory networks, neurons, colloids, ferrofluids, chemical reactions, memristive devices, mycelium, proteinoids, graphene-based materials, and quantum systems. Together they examine the fundamental principles of information processing beyond silicon while highlighting emerging applications in artificial intelligence, neuromorphic engineering, molecular electronics, soft robotics, sensing, and adaptive materials. This book serves as an authoritative reference for researchers, graduate students, and practitioners interested in the future of computation and intelligent matter.