Highly efficient two-photon absorbing polymers may eventually be used for 3-D optical data storage and myriad other applications including biomedical imaging. A group led by Joseph W. Perry and Seth R. Marder of the University of Arizona at Tucson have detailed their findings in the March 4 issue of Nature. When pulsed with laser light, these compounds absorb photons two at a time and can cause chemical or physical changes with resolution in three dimensions. The chemists' experiments reveal that lasers used in industry are powerful enough to excite the photon-absorbing molecules.