In this work, granules developed from UASB reactors that treat different types of wastewaters (ethanol, carbohydrates and protein-based synthetic wastewaters) were studied. Granule parameters (size distribution; density; settlement characteristics; elemental composition; acidogenic and methanogenic activities) were analyzed along with micro-organisms identified by FISH to better understand granule behavior and its formation process. Micro-organisms distributions in anaerobic granules are highly dependent on the type of treated wastewater. Granules developed in a UASB reactor that treats wastewater with a high content of carbohydrates presented high acidogenic bacteria colonization. Members of Methanosaetaceae were the dominant methanogens in the studied granules, and Methanobacteriales appear to be co-dominant in the granules developed with carbohydrates and protein-based wastewaters.