Biohydrogen production from various organic wastes, wastewaters and biomass has been widely studied due to the higher production rates and fundamentals and technologies have also been well developed and heavily documented through diverse laboratory-scale bioreactors. Recently, research has been geared to the concomitant production of biohydrogen and methane which is so called "biohythane". One-stage and two-stage (bio-(2)(H) + bio-CH4) methods are the main biohythane production methods and this field of research for probing into green biofuels is gradually gaining ground. In this paper, the salient aspects of biohythane research at the present time are revisited and the research success and latent promise of biohythane are highlighted based on the findings of the relatively few publications in this area. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.