Although entrepreneurship has started to receive significant institutional support throughout the world, very few entrepreneurs manage to successfully grow their organizations. To investigate this problem, this thesis takes its point of departure from an entrepreneurial growth perspective to study the role of the founding entrepreneurs in the transformation from micro enterprises to small firms. The transformation is conceptualized as a first step towards future growth and empirically investigated by analyzing qualitative data from case studies of agribusiness and food entrepreneurs in Tanzania. The qualitative approach allows for an in-depth exploration of an understudied process in a relevant but little investigated context. The resulting four articles of the thesis provide insights into the processes through which entrepreneurs learn to handle their growing businesses in tough environments that provide even successful microentrepreneurs with little guidance on how to manage and organize a small firm. Data analysis focus of their behaviors, emotions, and cognitions in response to experiencing internal and external growth challenges. The findings indicate that what entrepreneurs think, feel, and do about multiple business ownership and management problems influence their strategies and the building of managerial and organizational capabilities. This suggests that scholars and practitioners need to pay more attention to the microfoundations and microprocesses underpinning growth when designing entrepreneurship studies and support programs.