Charles Babbage's Analytical Engine (1837): Babbage's concept of a mechanical computer, the Analytical Engine, laid the groundwork for modern computing.
Ada Lovelace's Algorithm for the Analytical Engine (1843): Lovelace wrote the first algorithm intended for processing by a machine, creating the first computer program.
Ignaz Semmelweis's Handwashing Theory (1847): Semmelweis proposed handwashing to prevent the spread of disease, but his ideas were rejected by the medical community initially.
Louis Pasteur's Germ Theory of Disease (1850s): Pasteur's proposal that microorganisms cause disease was initially ridiculed but later revolutionized medicine and food safety.