In everyday language the terms psychology and psychological are used in very different meanings, without a clear definition of what the terms refer to. This article is an attempt to meet the need for clarification of the content and boundaries of psychology as a scientific discipline. This is a prerequisite for real scientific contribution to progress in cross-disciplinary research and to decision making in societal and cultural processes. Applying a holistic – interactionistic view as the frame of reference for planning, implementation, and interpretation of single studies, the target of theoretical and empirical analyses is the human psychobiological and social being in continuous interaction with his/her proximal and distal environment.