This paper describes the issue of piconet interconnection for Bluetooth technology. These larger networks, known as scatternets, have the potential to increase networking flexibility and facilitate new applications. While the Bluetooth specification permits piconet interconnection, the creation, operation and maintenance of scatternets remains open. In this paper, the research contributions in this arena are brought together, to give an overview of the state-of-the-art. First, operation of the Bluetooth system is explained, followed by the mechanism for link formation. Then, the issue of piconet interconnection is considered in detail. Processes for network formation, routing and intra- and inter-piconet scheduling, are explained and classified. Finally, the research issues arising are outlined.