If you click on the Google Doodle seen today in some parts of the world, a gloved hand inoculates six Petri dishes in which bacterial cultures then grow. Hovering over those dishes then reveals the source of the microbes — a stinky sock, an oft-touched doorknob, and a dirty sponge, among others.
All this is to honor Julius Richard Petri, whose 161th birthday would have been today. Petri died in 1921 at the age of 69.
As the Guardian notes, "Petri was not the first to use agar, a substance made from algae, to culture bacteria but he invented the standard dish in which it was done. The Petri dish allowed for the better identification of bacteria and the diseases they caused."