This review presents the development of micro-sized microbial fuel cells (including mL-scale and mu L-scale setups), with summarization of their advantageous characteristics, fabrication methods, performances, potential applications and possible future directions. The performance of microbial fuel cells (MFCs) is affected by issues such as mass transport, reaction kinetics and ohmic resistance. These factors are manipulated in micro-sized MFCs using specially allocated electrodes constructed with specified materials having physically or chemically modified surfaces. Both two-chamber and air-breathing cathodes are promising configurations for mL-scale MFCs. However, most of the existing mu L-scale MFCs generate significantly lower volumetric power density compared with their mL-counterparts because of the high internal resistance. Although mu L-scale MFCs have not yet to provide sufficient power for operating conventional equipment, they show great potential in rapid screening of electrochemically microbes and electrode performance. Additional possible applications and future directions are also provided for the development of micro-sized MFCs. (C) 2010 Elsevier Ltd. All rights reserved.