Progress in evaporative cooling of alkali atoms. The combination of laser cooling and evaporative cooling of alkali atoms was the essential technique for the observation of BEC in dilute atomic gases. This diagram shows all experiments reported until the end of 1996 on evaporative cooling of alkali atoms. The number of atoms in the lowest quantum state is proportional to the so called phase-space density, and has to exceed a critical number of 2.612 to achieve Bose-Einstein condensation.