March 2, 1995, was a red-letter day for researchers at the Fermi National Accelerator Laboratory near Batavia, Ill., and for their colleagues around the world. At a dramatic press conference, two teams of Fermilab investigators jubilantly announced that there was no longer any serious doubt that they had discovered what may be nature's last missing building block of matter, a subatomic particle known as the top quark. The announcement, however, hardly came as a surprise. At an earlier press conference, in April 1994, one of the research teams had reported suggestive, though not convincing, evidence that it had found the top quark. What had changed in the intervening months was the degree of certainty regarding the existence of the elusive particle. By March 1995, three times as much data had been collected to strengthen the case, and a second team had compiled similar experimental results.

Fermilab particle physicists—investigators of matter at the smallest levels—emphasized that the finding, though significant, didn't point to anything new or unexpected. Researchers in the field had been convinced for years that the top quark had to exist—they simply hadn't been able to find it. Moreover, the discovery of the top quark did not signal the opening of an exciting new era of research, but rather the conclusion of what might be the last chapter in the age-old quest for the basic building blocks of matter.