This book aims to give students a broad perspective of current understandings of the basic structures of matter as scientists have probed ever deeper levels from atoms, to the nucleus, on to leptons, quarks, and gluons, along with the necessary introductory quantum mechanics. Interwoven in the material are historical developments and challenging future directions. Beyond a broad understanding of atomic, nuclear, and particle physics, it is hoped that students will early in their studies appreciate the uncertain path of success and failure, opportunities seized and opportunities missed and the roles of chance and intuition by scientists in the unfolding human drama of scientific discovery. By working through some of the issues and struggles that occurred in the development of modern physics, students will better understand the material as well as learn how science works. Several significant historical developments are presented that are not found in any textbooks. Throughout the book, students are encouraged to reflect on problems and to ask questions.