The goal of this work is to present a specific focus on one of the main players in the innovation ecosystem: the Business Angels and their organizations. At general level, the thesis will address the main trends and characteristics of Business Angels, who in addition to financial support also want to provide more practical help to improve the companies they invest in and so be an active part of them. Specifically, it is intend to further study the organizational and investment structures in which they operate, such as BANs (Business Angel Networks) and BAGs (Business Angel Groups). Therefore, after a mention of the innovation context, several issues addressed in academic studies over the past decades will be examined to bring out the peculiarities in the emergence of Business Angel organizations.