Steven Chu, at Bell Laboratories, develops in 1985 a technique to slow and cool atoms using laser beams arranged in opposite directions: when an atom moves toward a laser beam tuned slightly below the atom's absorption frequency, the Doppler effect makes the atom perceive the light at exactly its absorption frequency, causing it to absorb photons that slow its motion in that direction; applying six laser beams from all directions makes it possible to bring atoms almost to a complete stop, effectively cooling them to extraordinarily low temperatures, a technique Chu calls "optical molasses" for the viscous resistance the atoms seem to experience. William Phillips, at the National Institute of Standards and Technology (NIST), refines the technique and experimentally discovers that atoms cool even below the previously calculated theoretical limit, an unexpected finding that drives later theoretical advances explaining the phenomenon. Claude Cohen-Tannoudji, at the École Normale Supérieure in Paris, develops the theoretical framework explaining this below-limit cooling through subtler quantum mechanisms, and perfects additional, even more efficient cooling techniques. These combined techniques allow atoms to be cooled to microkelvin temperatures — millionths of a degree above absolute zero — and prove to be the indispensable technical step that would make possible, a decade later, the creation of the first Bose-Einstein condensate and the development of atomic clocks of unprecedented precision.