Florence Nightingale's environment theory emphasizes the importance of the external environment in patient recovery, detailing physical, psychological, and social factors that can influence health outcomes. Her pioneering work during the Crimean War and publication 'Notes on Nursing' laid the foundation for nursing education and practices focused on sanitation, ventilation, and the overall environment. Nightingale's theory remains relevant in modern nursing by emphasizing the manipulation of environmental factors to enhance patient care and well-being.