With more and more organisations accepting social media into the workplace as an integral part of professional practice and group communication, understanding what exactly happens when enterprise social networks suddenly emerge in the workplace, brought in on initiative of employees in a self organising manner, is increasingly important. In this paper we present an analysis of enterprise based-short message communications shared across the Yammer enterprise social network at the international service consultancy Capgemini. We concentrate on conversations during the first nine months of uptake with a focus on self-referential communication where users convers about Yammer itself. A time-trend analysis of conversation types leads to the identification of what we term the SNEP model, the Social Network Emergence Process that captures the phases in which the social network emerged over time. The study for the first time allows to unpack in detail the often-discussed emergence aspect of enterprise social media, in terms of sense-making, user experimenting, norming behaviour, and network diffusion. The identified SNEP model is useful for managers who want to understand what happens when social media initiatives suddenly erupt into existence in their organisations.