Introduction to Matter and Radiation is a comprehensive book that illustrates the basic concepts of matter and radiation in physics. This book is written for students who are following the G.C.E (A/L) physics, physics teachers, first-year undergraduate students, and those interested in the important concept of matter and radiation in physics. It covers the fundamental topics in modern physics, nuclear physics, and elementary particle physics. The main objective of this book is to present the subject material in a simple and lucid style so that it can be easy to comprehend the relevant concepts and learn the techniques to find the solution to problems. This book has nine chapters covering various aspects of matter and radiation. Each chapter includes numerous well-labelled illustrations, drawings, graphs, and tables. In order to give an opportunity for the learner to examine his/her understanding of the concepts behind the subject and to enlighten the content in a more profound sense, several questions in the form of activities are included in all chapters. In addition, to improve problem-solving techniques, the questions have been framed in the following categories: conceptual questions, numerical questions, and practice questions. These questions are of varying difficulty and are carefully structured to guide the user in recognizing concepts and principles. These questions are included at the end of each chapter. Answers to most of the questions are given at the end of the book.