Hermann von Helmholtz was a 19th-century German physician and physicist known for his contributions to various fields, including thermodynamics, optics, and physiology. He is best recognized for formulating the law of conservation of energy, which states that energy cannot be created or destroyed, only transformed from one form to another. His work laid the foundation for modern physics and helped bridge the gap between physical sciences and biology. In addition to his scientific achievements, Helmholtz invented the ophthalmoscope, an instrument that allows doctors to examine the interior of the eye. He also conducted significant research on auditory perception, exploring how humans perceive sound. His interdisciplinary approach influenced many areas of science and medicine, making him a pivotal figure in the development of modern scientific thought.