Niels Bohr's most-noted contributions to contemporary thought center around his work with quantum theory. His atomic model of 1913, his complementarity approach to quantum mechanics, and his ensuing lifelong debate with Albert Einstein have all received extensive attention from physicists, historians, and philosophers alike. Yet Bohr's scientific creativity was not limited to atomic phenomena and quantum mechanics. He continued to blaze new paths into uncharted territory during the 1930s and 1940s as an early leader in the developing field of nuclear physics. This collection of original work, however, has garnered far less attention from Bohr scholars than has his well-known work with non-relativistic quantum mechanics.