Louis Pasteur was born on 27 December 1822 in Dole, Jura, France, into a Catholic family of modest means. He was the third child of Jean-Joseph Pasteur and Jeanne-Etiennette Roqui. The family relocated to Marnoz in 1826 and then to Arbois in 1827. Pasteur began his education in primary school in 1831, where he struggled with dyslexia and dysgraphia. Initially an average student, he showed more interest in fishing and sketching than academics. He attended the Collège d'Arbois and later the Collège Royal at Besançon, where he earned a Bachelor of Letters degree in 1840. He then pursued a degree in science, passing the baccalauréat scientifique in 1842 with a mediocre grade in chemistry.In 1843, Pasteur entered the École Normale Supérieure in Paris, where he studied under prominent scientists. He earned his licencié ès sciences degree in 1845 and became a professor of physics at the Collège de Tournon in 1846. He later returned to the École Normale Supérieure as a graduate laboratory assistant and submitted his theses in chemistry and physics in 1847. Pasteur became a professor of chemistry at the University of Strasbourg in 1848, where he met and married Marie Laurent in 1849. They had five children, but only two survived to adulthood.Pasteur's career advanced as he became the chair of chemistry at the University of Lille in 1852, where he began his studies on fermentation. He moved to Paris in 1857 as the director of scientific studies at the École Normale Supérieure, implementing reforms that improved scientific standards. He was appointed professor of geology, physics, and chemistry at the École nationale supérieure des Beaux-Arts in 1863 and later became the chair of organic chemistry at the Sorbonne in 1867. In 1887, he established the Pasteur Institute, which he directed until his death.Pasteur's early research focused on molecular asymmetry, particularly the properties of tartaric acid. He discovered that certain crystals could rotate polarized light, leading to the concept of molecular chirality. His work laid the foundation for structural chemistry. He also investigated fermentation, demonstrating that yeast was a living organism responsible for the process, thus refuting the theory of spontaneous generation. His experiments showed that microorganisms caused spoilage in beverages and led to the development of pasteurization, a method of heating liquids to kill bacteria.In the 1860s, Pasteur's research contributed to the germ theory of disease, which posited that microorganisms cause infections. He conducted experiments that demonstrated the role of germs in disease transmission, influencing practices in hygiene and surgery. His work on silkworm diseases, particularly pébrine and flacherie, established methods for preventing these infections, significantly impacting the silk industry.Pasteur's vaccine development began with chicken cholera, leading to the creation of vaccines for anthrax and rabies. His work on anthrax involved attenuating the bacteria to create a vaccine, which he successfully tested on sheep and cattle. The rabies vaccine was developed using weakened virus strains and was first administered to a human, Joseph Meister, in 1885, resulting in a successful outcome.Throughout his career, Pasteur faced controversies regarding his methods and claims. He maintained secrecy about his laboratory practices, which led to criticisms of his experimental ethics. Despite these controversies, he received numerous awards and honors for his contributions to science, including the Copley Medal and the Grand Cross of the Legion of Honor.Pasteur died on 28 September 1895, and his remains were interred in a vault at the Pasteur Institute. His legacy includes the establishment of the Pasteur Institute, which continues to advance research in microbiology and public health. His discoveries have had a lasting impact on medicine, hygiene, and the understanding of infectious diseases.