*Image Credit: Wikipedia Few discoveries in the history of medicine could be said to have had more of an impact than that of bacteria. Antonie van Leeuwenhoek, the Dutch scientist and Father of Microbiology who deserves credit for finding them and many other single-celled structures, died on August 26, 1723 at the age of 90. Along with Englishman Robert Hook, van Leeuwenhoek would be one of the first people to comprehend the vast amount of tiny life moving existing all around us through the use of microscopes. Born in Delft, Holland, van Leeuwenhoek grew up with a curious mind and a knack for business. An early interest in microscopes led him to pull them apart to determine how he might produce a more powerful lens to allow observers to further magnify their subjects. Almost by accident, he realized he could create tiny glass spheres with astounding rates of magnification by heating a small rod of glass and stretching it into a thin string, then reinserting one end into the flame. The simplicity of the method – which meant creating better lenses could be done in significantly less time – led him to believe others would forget his place in the advance of microscopes. Resolved to be remembered, van Leeuwenhoek hid his technique from the world, letting people think he was merely very hard-working. (It wasn’t until the 1950s that others were able to replicate his work.) As he began to use his proprietary equipment to observe the world, van Leeuwenhoek noticed minuscule particles that seemed to have lives of their own. Calling them animalcules, he had stumbled upon the microorganisms we know today – bacteria and spermatozoa, in particular. Turning the tools on the human body, he soon noticed muscle fibers and the slender blood vessel networks called capillaries that deliver nutrients to and remove waste from tissues. Having observed such phenomena, van Leeuwenhoek hoped to gain entry into the most famous scientific organization of his day: the Royal Society of London. Once he learned of its existence from a colleague, he submitted his observations regularly and had some of his first papers – drawings of “bee mouthparts and stings” – published in 1673. When he offered his notes on single-celled organisms in 1676, however, the Society suspected van Leeuwenhoek of fraud. Without any proof of such life, the group believed his work to be a hoax. Four years later, after finally convincing the Society to send a delegation to Delft to test his observations, his reputation was restored and he gained full membership in the exclusive club. A prolific writer, van Leeuwenhoek would go on to compose well over 500 letters to peers over the remaining five decades of his life, working right up until his death and even relating the particulars of his own condition as he lay dying. Despite being an amateur – he had no formal scientific education – van Leeuwenhoek made one of the most important finds in the history of medicine and revolutionized the way scientists looked at both the large and the small.