By year 1911 radioactivity had been discovered for over a decade, but its origin remained a mystery. Rutherford's discovery of the nucleus and the subsequent discovery of the neutron by Chadwick started the field of subatomic physics -- a quest for understanding the fundamental constituents of matter.This book reviews the important achievements in subatomic physics in the past century. The chapters are divided into two parts: nuclear physics and particle physics. Written by renowned authors who have made major developments in the field, this book provides the academics and researchers an essential overview of the present state of knowledge in nuclear and particle physics.