When the Federal Bureau of Investigation announced it had cracked the long-unsolved anthrax case, the turning point cited by the bureau was its identification of a laboratory flask as the source of the anthrax.

The dots, or in this case more than a thousand separate anthrax samples, were connected with the help of a group of scientists working secretly for some seven years. They succeeded by using a combination of new techniques not even invented in late 2001 when the anthrax-laced letters were sent, and that most old-fashioned attribute of expert scientists and detectives: a trained eye.