Bioelectrochemical system (BES) has become widely recognized as a leading technology for a variety of applications, including electricity generation, wastewater treatment, hydrogen evolution, and chemical synthesis. To power BES, freely available biomass has been extensively employed as an energy source, producing electrical current and biofuels through biocatalytic reaction of diverse functional bacteria. Under the BES family, several advancements for specific applications, such as microbial fuel cells (MFC), microbial electrolysis cell (MEC), plant microbial fuel cell (PMFC), and microbial solar cell (MSC), have been successfully created and improved in related research domains. This chapter briefly reviews BES applications and their advancements concentrating on biomass utilization, light reactions, and the functional microorganisms that drive BES for electricity generation, biofuel production, and waste treatment.