Julian Schwinger was an American theoretical physicist, born on February 12, 1918, and passed away on July 16, 1994. He is best known for his contributions to quantum electrodynamics (QED), a field that describes how light and matter interact. Schwinger's work, alongside that of Richard Feynman and Sin-Itiro Tomonaga, earned him the Nobel Prize in Physics in 1965. Schwinger developed the S-matrix formulation of quantum mechanics, which provides a framework for understanding particle interactions. His research laid the groundwork for many modern advancements in particle physics and has influenced various areas of theoretical physics, making him a key figure in the scientific community.