Since 2003 the research on Personal Learning Environments has increased. These environments support problem based, situated and informal learning in social networks within organisations and educational institutions and in subject related communities. The EU project MATURE enhanced this idea with the concept of a Personal Learning and Maturing Environment (PLME), which shall support and foster learning and knowledge maturing. In this paper, we present a model that describes the maturing of knowledge and informal learning. Based on an example of changing a university study course, we present the personal, community and organisational perspective on knowledge maturing and informal learning. This leads to a derivation of requirements for a PLME implementation.