In this target article, we argue that personality processes, personality structure, and personality development have to be understood and investigated in integrated ways in order to provide comprehensive responses to the key questions of personality psychology. The psychological processes and mechanisms that explain concrete behaviour in concrete situations should provide explanation for patterns of variation across situations and individuals, for development over time as well as for structures observed in intra-individual and inter-individual differences. Personality structures, defined as patterns of covariation in behaviour, including thoughts and feelings, are results of those processes in transaction with situational affordances and regularities. It cannot be presupposed that processes are organized in ways that directly correspond to the observed structure. Rather, it is an empirical question whether shared sets of processes are uniquely involved in shaping correlated behaviours, but not uncorrelated behaviours (what we term ‘correspondence’ throughout this paper), or whether more complex interactions of processes give rise to population-level patterns of covariation (termed ‘emergence’). The paper is organized in three parts, with part I providing the main arguments, part II reviewing some of the past approaches at (partial) integration, and part III outlining conclusions of how future personality psychology should progress towards complete integration. Working definitions for the central terms are provided in the appendix.