Although complexation of charged particles induced by polyions of opposite charge is a well-known phenomenon, the possibility of obtaining equilibrium clusters stuck together by flexible polyions, which act as an electrostatic glue, is not completely recognized. In this Letter, we call attention towards the behavior of polyions in attaching together charged particles, by means of controlled electrostatic interactions. As an example, we present some features of equilibrium clusters composed of cationic liposomes built up by DOTAP and glued up by an anionic polyion, polyacrylate sodium salt. We discuss briefly some applications in nanostructure science and biotechnology. (c) 2005 Elsevier B.V. All rights reserved.