What is knowledge? Cognitive, social, and educational psychologists define it as a collection of information or facts and their meaning in relation to each other that is stored in the brain, but in each of these psychological areas, a different facet is highlighted. Cognitive psychologists study knowledge as the construction and representation of information in memory. Social psychologists study knowledge as the influence of feelings, beliefs, and attitudes on behavior. Educational psychologists study knowledge as the improvement of performance through training, instruction, and teaching. Currently, encouraged by the replication crisis and the epistemic philosophical views, more psychological researchers are beginning to shift their focus towards knowledge as an actual-world phenomenon, which especially has much ground in common with the discipline of cognitive science (i.e., artificial intelligence and the neurosciences). However, this anew direction in the psychological study of knowledge is complicated, in that researchers have to reckon with its dynamical nature in the actual world. The dynamical character of knowledge involves that it (a) changes over time in various manners, (b) is an experientially personalized construction, and (c) is capriciously interacting with situational influences. The difficulty in scientifically observing knowledge as an actual-world phenomenon encompasses (a) how individuals retrieve knowledge via cognitive, social, and emotional considerations, (b) how knowledge has an interaction with the individual’s physique and behavioral expression modes, and (c) how knowledge has an interaction with the present situation or surrounding environment. In this article, I will discuss present theories, views, and scientific evidence and findings in psychology, philosophy, and cognitive science regarding knowledge as an actual-world phenomenon with the aim to provide for methodological suggestions for future psychological research.