Ours is an age of incredible breakthrough in science and technology. Man has blazed a trail into outer space, built 'thinking machines' and made a giant progress, but yet he is not fully aware of what exactly is inside the atom. The nucleus, however remains somewhat a riddle. How are the nucleons packed within a tiny nucleus? What is the nature of nuclear force? How can the nucleus be smashed open to harness the tremendous energy, it yields? The master theorists and experimenters have designed and built huge machines called accelerators to probe into the nucleus and solve nuclear mysteries. Particle science has gained prominence and has emerged as exciting field of research. It is imperative, therefore, that the young people interested in science read this book. It is our firm belief that this book will also help many with the crucial choice-their further studies and future occupation. We feel this will make very interesting reading without unnecessarily taxing the mind, but at the same time imparting the knowledge required to complement a prescribed course on the topic.