This review provides an overview of microbial fuel cells (MFCs) and their applications in bioelectrochemical systems (BESs). MFCs have gained significant attention for their ability to convert organic waste into electricity through microbially catalyzed anodic and microbial/enzymatic/cabiotic cathodic electrochemical reactions. The review covers the history of MFCs, the development of BESs, including microbial electrolysis cells, microbial desalination cells, and microbial electrosynthesis cells. It discusses the electroactive biofilms and electron transfer mechanisms involved with solid electrodes, the materials used as anode and cathode catalysts, and the challenges and advancements in MFC technology. The review also highlights the practical implementation of MFCs, such as their use in wastewater treatment and energy harvesting. Despite the progress, several challenges remain, including the low energy output and the need for further research on electron transfer mechanisms and electrode materials. The review concludes by emphasizing the potential of MFCs in sustainable energy solutions and the ongoing efforts to improve their performance and applicability.This review provides an overview of microbial fuel cells (MFCs) and their applications in bioelectrochemical systems (BESs). MFCs have gained significant attention for their ability to convert organic waste into electricity through microbially catalyzed anodic and microbial/enzymatic/cabiotic cathodic electrochemical reactions. The review covers the history of MFCs, the development of BESs, including microbial electrolysis cells, microbial desalination cells, and microbial electrosynthesis cells. It discusses the electroactive biofilms and electron transfer mechanisms involved with solid electrodes, the materials used as anode and cathode catalysts, and the challenges and advancements in MFC technology. The review also highlights the practical implementation of MFCs, such as their use in wastewater treatment and energy harvesting. Despite the progress, several challenges remain, including the low energy output and the need for further research on electron transfer mechanisms and electrode materials. The review concludes by emphasizing the potential of MFCs in sustainable energy solutions and the ongoing efforts to improve their performance and applicability.