Dr Raja Ramanna (1925-2004) was a visionary nuclear physicist and key figure in Indian nuclear and defence research. During his first term as director of the Bhabha Atomic Research Centre (BARC), India successfully tested its first nuclear device. Subsequently, Dr Ramanna served his nation in various roles, including as Secretary for Defence Research, Chairman of the Atomic Energy Commission, and the Minister of State for Defence as well as Member of Parliament. He also contributed tremendously to academic positions in IIT Bombay and the Indian Institute of Science, eventually becoming founder director of the National Institute of Advanced Studies (NIAS) in Bangalore. He was known to be a multifaceted person, with accomplishments in science, technology, policy and the arts. NIAS celebrated the centenary of his birth in January 2025. Edited by two eminent scholars from NIAS, this volume gathers contributions from various people who have worked with or associated with Dr Raja Ramanna. The chapter authors reflect on their encounters with Dr Ramanna and the institutions he led, while expanding on topics ranging from nuclear fission, defence science, technology policy, governance, philosophy and music, the last being a well-known lifetime interest of Dr Ramanna. Through the writings of the people Dr Ramanna influenced, readers gain a glimpse of his personality and actions, with many lessons to learn from his long life of service and research. This book is a suitable reading for students and researchers in nuclear physics and particle physics, as well as policymakers and officials in science and technology.