Peni­cillin is a type of antibi­ot­ic med­ica­tion that was first dis­cov­ered by Scot­tish biol­o­gist Alexan­der Flem­ing in 1928. It is pro­duced by a fun­gus called Peni­cil­li­um, and it works by killing or stop­ping the growth of bac­te­ria that cause infec­tions. Peni­cillin was the first antibi­ot­ic to be used on a large scale, and it rev­o­lu­tion­ized the treat­ment of bac­te­r­i­al infec­tions such as pneu­mo­nia and strep throat. It is still used today as a wide­ly pre­scribed and effec­tive antibi­ot­ic, although some strains of bac­te­ria have become resis­tant to it. The dis­cov­ery of peni­cillin is con­sid­ered one of the most impor­tant med­ical break­throughs of the 20th cen­tu­ry. The lab­o­ra­to­ry in which Flem­ing dis­cov­ered and test­ed peni­cillin is pre­served as the Alexan­der Flem­ing Lab­o­ra­to­ry Muse­um in St. Mary’s Hos­pi­tal, Padding­ton, in the City of West­min­ster, London.