Linus Pauling was the most important chemist, and arguably the most important American scientist, of the 20th century. From his description of the chemical bond to his discovery of the cause of sickle-cell anemia and his groundbreaking work with vitamin C, his work stretched the boundaries of chemistry, physics, biology, immunology, and more. Acclaimed science writer Tom Hager brings Pauling's wide range of scientific accomplishments vividly to life while also shedding light on Pauling's activities outside the scientific realm. He shows how Pauling used his popularity to advance political causes, particularly his opposition to the spread of nuclear weapons during the 1950s. Despite the troubles his political activism caused him, he remained unmoved in his dedication to making the world a safer place. His perseverance was rewarded with a Nobel Peace Prize in 1963, which along with his 1954 Nobel Prize in Chemistry, made him the only person in history to win two unshared Nobels.