What it took to discover bacteria in the 1670s

Humans will probably always underappreciate the microorganisms that live inside us and all around us, but the truth is that we live in their world. Not only did our evolution depend on an environment that microbes created, but microbes continue to influence our health in countless ways.

"Right from the start, we would have been surrounded by microbes, filled by microbes. Of course, we needed to evolve ways of negotiating with them, ways of exploiting the molecules that they were already putting out in the environment, of learning to learn in symbiosis with them," said Ed Yong, author of I Contain Multitudes: The Microbes Within us and a Grander View of Life.

As DNA sequencing technology invigorates the study of the human microbiome, we take a look at the first tool ever used to study microbes: the tiny microscopes of Dutch tradesman Antony van Leeuwenhoek. Check out the video above to learn how Leeuwnehoek became the first human to lay eyes on single-celled organisms.