There has been a considerable discussion in the past years on the similarities and differences between Clouds and Grid Computing. This included extreme positions whether Clouds are a pure marketing hype, or whether Grids became obsoleted by failing a wide commercial adoption as a resource sharing platform. Now, we can assess that neither is true nor necessary. Grids and clouds share many similarities as they both address questions concerning access to resources in a large-scale distributed environment. Thus, there is significant overlap between the two areas in the ways that infrastructures may evolve.