This article reports on a study into the integration of ICT for students' personal use in the secondary mathematics classroom through using small software applications on handheld computing devices (graphical calculators). The handhelds were networked through wireless hubs so that data, software and output can be shared and an interactive space created for whole-class interaction and discussion. It argues that personal access to ICT tools within the traditional classroom environment is vital to support and enhance learners' mathematical development and that integration is effectively initiated through the use of "microworlds". The initial outcomes of this study and a review of research carried out in the USA and Europe reveal the transformative potential of this technology for the mathematics classroom and other educational settings. (Contains 1 note and 1 figure.)