Graphene and its derivatives are heralded as 'miracle' materials with manifold applications in different sectors of society from electronics to energy storage to medicine. The increasing and widespread interest and use of graphene-based materials (GBMs) necessitates a comprehensive evaluation of the potential impact of these materials on human health and the environment. Here we discuss synthesis and characterization of GBMs as well as human and environmental hazard assessment of GBMs using in vitro and in vivo model systems with the aim to understand the properties that underlie the biological effects of these materials; not all GBMs are alike, and it is essential that we disentangle the structure-activity relationships for this class of materials.