QUANTUM HOLOGRAPHY, in which a pair of laser pulses reveals detailed information about an atom's state, has been used for the first time to control the shape of an atom wave, advancing prospects for tailoring an atom's exact properties. Classical holography, which makes 3D pictures, involves the use of an "object" and a "reference" laser beam. How these beams combine in a piece of film provides information on their relationship (specifically, their relative "phases"), allowing the eyes to build up a 3D scene. In quantum holography, an ultrashort laser pulse (playing the role of an object beam) first puts an atom into a combination of wavelike states, forming a "wavepacket." Shortly thereafter, a subsequent pulse (acting as the reference beam) creates a second wavepacket within the atom. These two wavepackets interfere. Ionizing the atoms and then measuring them at a detector can provide information about the phase relationships between the wavepackets, ultimately yielding details on the individual wavelike states. University of Michigan researchers (Tom Weinacht, 734-764-2344) have now demonstrated a feedback approach, in which they shine a pair of pulses on a gas of cesium atoms, measure the effect, and modify subsequent pairs of pulses until they get the cesium wavepacket they want. Such "wavepacket engineering" may enable scientists to prepare atoms and molecules which undergo precisely desired chemical reactions. (Weinacht et al., Nature, 21 January 1999; see also Physical Review Focus, 23 June 1998.)