This book contributes to the emerging research on the growth process of firms, with a focus on the expansion of small and medium-sized enterprises (SMEs). A comprehensive approach to the issue of small firm growth draws upon empirical findings of the characteristics and economic importance of high-growth enterprises and the extant base of theoretical approaches to the growth of firms, with an emphasis on the literature of firm boundaries (scope and size). Consequently, this research adopts a deductive approach to building the conceptual framework of SME growth by integrating the resource-based view of the firm and transaction cost theory. This integrative theoretical framework was tested by using the multi-case study method to conclude with a proposal of the model of the growth process of SMEs. The model explains the choices of high-growth entrepreneurs regarding contractual arrangements, portfolio development, sources of new products, and associated governance in the expansion process. Consistent with the heterogeneity of SME expansion, the research reveals three equifinal patterns of these choices instead of only one path. This book is valuable for bridging separate and divergent streams of the literature on firms’ growth, namely, entrepreneurship, microeconomics, and strategic management literature related to firm boundary decisions.