AbstractThe cover picture shows the size‐dependent photoluminescence from CdSe colloidal quantum dots that were investigated in the work [1]. Ultrafast photon echo experiments were undertaken in conjunction with simulations based on a realistic many‐body theory, shown in the picture, to ascertain the significance of many‐body contributions to the third‐order nonlinear response.The first author Anne E. Colonna undertook this research during a summer internship in the Department of Chemistry, University of Toronto. She is currently pursuing graduate studies at École Polytechnique, Saclay, in the Laboratoire d'Optique et Biosciences.The author Gregory D. Scholes is an Assistant Professor in the Department of Chemistry, University of Toronto. His research interests include synthesis and shape control of quantum dots, as well as the application of ultrafast laser spectroscopy to investigate the electronic structure of inorganic and organic semiconductors. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)