Venoms have evolved on numerous occasions throughout the animal kingdom. These 'biochemical weapon systems' typically function to facilitate, or protect the producing animal from, predation. Most venomous animals remain unstudied despite venoms providing model systems for investigating predator-prey interactions, molecular evolution, functional convergence, and novel targets for pharmaceutical discovery. Through advances in 'omic' technologies, venom composition data have recently become available for several venomous lineages, revealing considerable complexity in the processes responsible for generating the genetic and functional diversity observed in many venoms. Here, we review these recent advances and highlight the ecological and evolutionary novelty of venom systems. © 2012 Elsevier Ltd.