It used to be that growth was just the goal, or the outcome, of a company's operations, but under the influence of leading software companies, it has become more than that. Growth is now a company function in itself, with its own processes and tools and its own teams, working alongside marketing, sales or engineering teams. Growth is set to become a major field of management in the future. The purpose of this paper is to explore the fundamentals of how software startups think about growth, and to work up from there to the processes they use to drive exponential growth and the challenges they encounter. The processes, frameworks and tools presented in this paper are not always well understood, and not used widely enough outside of the community of startup marketers and growth professionals. That is why this paper was written to give a solid basic understanding of Growth to anyone wanting to learn about this emerging function. At the same time, I strived to make it inspiring for experienced growth professionals as well, by focusing my research on the challenges companies face when trying to create a highly performing growth team.