This chapter examines the theoretical underpinnings behind collection activities and illustrates the drivers for the practice and management of collection. It discusses the different types of sources in the commercial environment. The complications of imperfect intelligence requirements and unknown unknowns place a considerable obligation on the intelligence professional. Sources of information in intelligence encompass a wide range, and for ease of administration they have been divided into a number of categories. The communication and information revolution has made available a range of information beyond the dreams of intelligence professionals of previous generations. Social media is a key aspect of the information revolution and is a natural extension of the principle of information sharing that underpins the Internet. Human intelligence information can take a number of forms. It can be based on individual relationships, where an intelligence professional is known to the human source. The collection stage of the intelligence cycle can represent a daunting challenge.