In this engaging and accessible book, renowned science popularizer Isaac Asimov presents the latest understanding of one of the most elusive particles in the microcosm—the neutrino. Asimov traces the sequence of discoveries that led physicists to the neutrino’s revelation, explains how this tiny particle is detected, and explores its crucial role in the evolution of the universe. He also discusses the latest breakthroughs in neutrino physics, including the groundbreaking two-neutrino experiment. With clarity and passion, the author aims to paint a vivid picture of modern physics for the reader, without overwhelming with an excess of technical details. This book will appeal to a wide audience: students, educators, and anyone eager to stay updated on the frontiers of physics.