Werner Karl Heisenberg was a renowned German physicist who made significant contributions to the field of quantum mechanics in the 20th century. His name is synonymous with the uncertainty principle, a fundamental concept in quantum physics that states that the position and momentum of subatomic particles cannot be measured simultaneously with complete accuracy. Heisenberg also developed the matrix mechanics formulation of quantum mechanics and made ground-breaking discoveries in nuclear physics. His work on particle scattering and the atomic nucleus led to the development of the first nuclear reactor. Heisenberg's legacy has had a profound impact on modern physics, and his name is closely associated with some of the most significant scientific breakthroughs of the 20th century.