The word “hybrid” means that elements which usually do not go together or belong to different spheres get intertwined within one organisational being. In recent years the author of this contribution together with (see Evers and Laville 2004) or parallel to other colleagues (see Brandsen et al. 2005) has taken up this notion in order to describe organisations that in a way tie together characteristics, that get usually separated in state, market and third sector organisations. This contribution will in its first part sketch the background concepts and the special notion of the third sector as an intermediary sphere that is behind my concept of what hybrid organisation means. The second part of the contribution will once again summarise what I see as constitutive for hybrid organisations and clarify what difference it makes to those concepts, that draw clear demarcation lines between state, market and third sector organisations. In a third and final part open and controversial questions and challenges for further research will be sketched. Altogether this may allow for an overview on a topic I have hitherto dealt with in several publications.