Microbial fuel cells (MFCs) have been attracting increasing interest during the past decade as an energy-recovery wastewater treatment technology. The application of suitable low-cost cathode catalysts to improve the oxygen reduction reaction (ORR) and the development of low-cost separators are posing major challenges for the practical applications of MFCs. An ideal cathode catalyst should be scalable, durable, and cost-effective. Similarly, an anode is a crucial component of the setup, both structurally and functionally. It provides support for bacterial attachment and simultaneously acts as a sink for electrons from substrate metabolism. The poor performance of anodes in MFCs is still a major setback for their practical application. Successful anode modification for enhancing their biocompatibility is expected to increase the electricity generation efficiency of MFCs. More than 80% of the cost of MFCs is due to electrodes and separator material. This chapter addresses the principles, challenges, and opportunities of MFCs, which are attracting attention of researchers as an exciting new discipline at the nexus of microbiology and electrochemistry. This chapter also tries to consider the realm of low-cost solutions to the challenges faced by this technology, thus facilitating its scale up. © 2018 Elsevier B.V. All rights reserved.