Thirty-five years ago today, on January 31, 1990 (January 5, 1990 in the lunar calendar), Europe used the electron-positron collider to determine that there are only three kinds of neutrinos. On January 31, 1990, the European Center for Nuclear Physics used the 27-kilometer circumference of the "Lepper" electron-positron collider to study the total and partial widths of the decay of Z0 intermediate bosons by four experimental groups, and reliably determined that there are only three kinds of neutrinos.