When Antonie van Leeuwenhoek first peered into the realm of microorganisms in 1675, he launched a field of study that grew steadily over the years. Today, of course, the field is virtually exploding as new discoveries occur.

Carl Woese, a professor of microbiology at the University of Illinois' Urbana campus, has added significantly to this growing body of knowledge, and for this he recently was awarded the prestigious Leeuwenhoek Medal.

Given once a decade by the Science Division of the Royal Netherlands Academy of Arts and Sciences, the medal is awarded for outstanding contributions to the study of microbiology.

"Before I got into the game, microbiologists had no biogenetic evolutionary tree," Woese explains. "What I did was construct that tree."

In 1977, Woese rocked the microbiological world with a paper (Proceedings of the National Academy of Sciences, 74:5088-90) claiming that not two, but three distinct types of microorganisms existed, dispelling...