Aulus Cornelius Celsus was a Roman scholar and physician who lived during the 1st century AD. He is best known for his work, De Medicina, which is one of the earliest comprehensive medical texts. This work covers various aspects of medicine, including surgery, diet, and pharmacology, and is notable for its systematic approach to medical knowledge. Celsus's writings were influential in both ancient and later medical practices. His observations and methods laid the groundwork for future medical studies, and his emphasis on the importance of observation and experience in medicine is still valued today.