Chapter 2 revises some seminal definitions of ‘genre’ and key conceptualisations in genre theory, such as ‘genres as frames for social action’, ‘intended audiences’ and ‘communicative purpose(s)’. The intention is to introduce and reflect upon recent conceptualisations of web-mediated generified activity – for example, ‘genre remediation’, ‘transmediality’, ‘polycontextuality’ and ‘context collapse’, among others – from the perspective of structuration theory. This chapter also expands on Swales’s understanding of metaphors of genre to critically address the aspects of generic evolution, hybridisation and change. The chapter also critically reflects on the concepts of ‘language collusion’ and ‘language collisions’ and draws on the metaphors of genre(s) and language(s) ecologies to explain the emergence of new genres on the web, the evolution of traditional genres, the interdependence between traditional and new genres and, more importantly, the creation of complex genre assemblages that support multilingual science communication on Web 2.0.