This document discusses understanding maturity models through a structured content analysis of existing maturity models. It presents the methodology used, which was a structured content analysis of 16 maturity models from different domains. The analysis sought to better understand the concept of maturity modelling and inform future developments, particularly in the area of knowledge management. Key findings from the analysis include implications for defining concepts like what maturity means, what the maturing subject is, how models are used, and who uses them.