This is a journal issue invested in remarking more than once upon the undecidability hovering today around our getting into contact with ‘ubiquity’ or ‘pervasiveness’ as a potential to be further actualized in the fields of human-computer interaction (HCI), interaction design, and the cultural life worlds of information societies more generally. Affirming this undecidability is a necessity – since both of these alternatives are currently at stake, and since ‘ubiquity’ and ubicomp remain potentialities of whose actualization we are not yet sure, whether this is matter of an explicit articulation of the principal ideas or of the concrete lines of development and research making of this so many hands-on facts inherent in the interactions in our contemporary life worlds. In other words, the focus and special merit of this issue is not least to enter into the set of questions surrounding the notion of ‘interaction designs for ubicomp cultures’ – as something partaking of that which Michel Foucault would have called ‘a history of the present.’ This introduction gives a comprehensive account of current thinking and practice in this contemporary field of research in order to make a difference that makes a difference while the cultural and technical developments at stake are still undecidable, multiple, and emergent – at a fast pace, too.