The evolution of pure software systems remains a time-consuming and error-prone activity. But whatever the considered domain, recurring practices can be captured and reused to alleviate the subsequent amounts of effort. In this paper we propose to treat domain-specific problems-solutions pairs as first-class entities called "evolution styles''. As such, an evolution style is endowed with an instantiation mechanism and can be considered at different conceptual levels. Applied on arbitrary domains, an evolution style is intended to evolve a family of applications whereas its instances evolve given applications. The evolution style's format is a component triple where each component is highly reusable. In this way, evolution styles are scalable knowledge fragments able to support large and complex evolutions, readily available to be played and replayed.