Julius was a bacteriologist who is best known for his invention of the Petri dish. The Petri dish, also known as a Petri plate, is a shallow cylindrical glass lidded dish that is used to culture cells and bacteria. Julius developed the Petri dish in 1887 while working as an assistant in the Imperial Health Office in Berlin. His invention revolutionized the field of microbiology and allowed scientists to study bacteria in a controlled environment.