It is widely believed that human interaction is much more regular than has yet been detected. What kinds of hidden regularities exist is, however, unsettled. In this paper a structural hypothesis is proposed where each continuous human interaction is seen as the performance of a set of a particular type of temporal patterns. Some of these repeated intra- and inter-individual real-time behavior patterns may be mutually exclusive in time while others may overlap in various ways. Perceptual limitations making such patterns hidden to the naked eye are illustrated. A computerized detection method and illustrative empirical findings from various types of face-to-face interactions in children and adults are presented. The specially developed pattern detection and analysis software, THEME, is also shortly described.