METAL INCLUSIONS COME IN SPECIAL SIZES. Gold does not come out of the ground as ingots, but rather as misshapen lumps ensconced in a rocky ore. One can ask whether, in general, nature dictates the size and shape of chunks of one element embedded in another solid. This issue is especially important at the microscopic level since the melting point of some materials can be raised or lowered considerably by burying particles of one type within the sample. A Berkeley-Copenhagen- Rio de Janeiro collaboration (contact Uli Dahmen, uli_dahmen@macmail.lbl.gov) has now shown, for the first time, that nanoscopic three-dimensional lead inclusions, having come to equilibrium inside an aluminum matrix, assume only special ("magic") sizes. These preferred shapes, the researchers believe, are imposed by the crystalline mismatch between the two elements. In time, this magic-size phenomenon might be useful for tailoring specific thermodynamic, magnetic, electronic, or optical properties. (U. Dahmen et al., Physical Review Letters, 20 January 1997.)