This conclusion presents some closing thoughts on the concepts discussed in the preceding chapters of this book. The book eradicates the whole idea of ill-defined constructs such as 'identity'. It retains the concept by re-defining and extending it, so that all of its different facets can be incorporated together. The book shows that social scientists still look at many variables within the individual and their social environment, and create interventions which centre on these, without considering the non-social agents that might have important interactive effects on human development. All this suggests that there is an urgent need for intra-disciplinary and inter-disciplinary discussion and debate as to how new approaches can be addressed and collaboration realistically initiated. It seems clear that the challenge for future research on adolescent transitions is to explore and understand individual development in a changing world and this will require novel, inter-disciplinary investigations to 'boldly go' innovatively forward in theory-building, devising research questions, and deriving methodologies.