The paper analyzes the historical development and key features of the HUMINT discipline, i.e. data collection through human sources. The aim of the paper is to define the concepts and methods of HUMINT operations in order to provide a general insight into the activity and to illustrate its development and adaptation from ancient civilizations to the present day. Historical examples will highlight the importance of this oldest intelligence discipline, while also addresing ethics that is an essential part of the intelligence profession. In the final part of the paper, the challenges of the modern era are mentioned that affect the further development of the discipline. Ulitmately, the goal of this paper is to demonstrate, through the analysis of the long history of data collection through human sources and the evolution of tactics and techniques, the usefulness of the HUMINT discipline and the reason why it is one of the most important intelligence disciplines.