Number 191 (Story #2), August 23, 1994 by Phillip F. Schewe and Ben Stein PLASMA CRYSTALS, macroscopic ensembles of dust particles held in a crystal-like array by a plasma of weakly ionized argon atoms, have been devised by a Garching-Cologne-Iowa team of physicists (H. Thomas et al., Physical Review Letters, 1 August). The dust assembly, consisting of 7-micron plastic balls, is contained between two electrodes and illuminated by a laser beam. Even with the unaided eye, one can see that the particles arrange themselves regularly in as many as 18 planes parallel to the electrodes. Plasma crystals might be useful in modeling interstellar clouds, which are dusty plasmas, and in plasma-assisted manufacturing techniques, prominent in the microelectronics industry. (Science News, 6 August; Nature, 11 August.)