Surely, we have scientists to thank for the spectacular discoveries made every day in medical science. But scientists themselves may have the petri dish to thank.

The well-known shallow and lidded cylindrical plastic plates are often used to grow bacterial cultures, serving a variety of uses, such as testing the virulence of bacterial cultures or examining the efficacy of antibiotic drugs in development. They also serve good use in food safety tests, helping to ensure whether particular types of bacteria are harmless or even useful.

However, the Petri dish we know today did not start out this way. Enter Julius Richard Petri, a German microbiologist, who in the late 19th century worked as an assistant to bacteriologist, Richard Koch. The laboratory based much of its research on bacterial growth on agar, a jelly-like yet solid substance that provides a substrate for bacteria to grow in easily examined conditions, at it's clear and bacteria remains on its surface.

The original method was to pour the agar into an open glass dish and cover it with a bell jar. This proved to be detrimental to results because, in order to observe the dish's contents under a microscope, the cover had to be removed, exposing the studied bacteria to uncontrolled conditions and contaminants like dust, human breath, or even hair.

The scientists noted that the bacterial colonies could be more easily observed if they were spread out on a flat surface, like a plate, and that something needed to be done about the risk of contamination.

In 1887, after six years of using agar medium on the open dishes and getting questionable data, Petri had the idea of placing a slightly larger clear glass dish over the original dish to protect it from outside conditions.

The invention was simpler and more compact than the bell jar and allowed for more efficient experiments, since contamination was no longer as prevalent. The cover of these new dishes, dubbed Petri dishes, could stay on at all times to protect experiments from confounders. Similarly, the cover was transparent and as close as possible without touching the media or the experimental bacteria, ensuring one could observe the dish, with or without a microscope, easily.

Petri, and his dish, moved on to work in a tuberculosis lab in Germany and published nearly 150 papers regarding his findings on the spread of disease and appropriate hygienic practices. The dish was used in a number of studies that pushed health care to the caliber that it is at today.

For example, when scarlet fever bacteria, Streptococcus, was found to grow in milk in the late 1920s, studies were performed on Petri dishes to show the importance of keeping milk refrigerated to ensure people's health. Similarly, during the 1918 Influenza Epidemic, scientists used the dishes to prove that the bacteria causing tuberculosis was not the same pathogen causing the flu in so many people; comparisons of bacteria found in infected people were important for this finding and for treatments thereafter. Most recently, in a 2012 study, a group of Canadian researchers made models of the pancreas on Petri dishes to better identify causes of pancreatic cancer.

The plates are now made of disposable plastics, again to avoid contamination, and are used by labs around the globe for various studies in diverse fields. Today marks Julius Richard Petri's 160th birthday, and nearly 130 years of the use of his impactful invention.