We tend to believe that thinking happens only in the brain-that intelligence requires neurons, synapses, and gray matter. But what if the ability to solve problems, remember the past, and plan for the future existed long before brains evolved? Intelligence Without Brains challenges our most fundamental assumptions about life, introducing the Search for Unconventional Terrestrial Intelligence (SUTI). This book is essential reading for science enthusiasts, technologists, and anyone curious about the invisible cognitive networks that keep us alive. Readers will journey into the microscopic realm where cells communicate via bioelectric networks to build complex bodies and repair damage. You will discover how flatworms regenerate lost heads by accessing a stored anatomical memory, how slime molds solve mazes without a single neuron, and why cancer is actually a failure of cellular communication. By exploring the cutting-edge science of developmental biology and synthetic xenobots, this narrative reveals that life is not merely a chemical machine, but a programmable decision-maker. Avoiding metaphysical speculation about consciousness, this book grounds its arguments in rigorous experimental evidence and systems science. It offers a clear, accessible framework for understanding how simple biological loops create complex behaviors. This is a guide to the new frontier of biology, where we stop asking how life looks and start asking what life knows.