The Differentiated Model of Giftedness and Talent (DMGT) presents the talent development process (P) as the transformation of outstanding natural abilities, or gifts (G), into outstanding systematically developed skills which define expertise, or talent (T) 3 in a particular occupational field. This developmental sequence constitutes the heart of the DMGT. Three types of catalysts help or hinder that process: (a) interpersonal (I) catalysts, like personal traits and self-management processes; (b) environmental (E) catalysts, like socio-demographic factors, psychological influences (e.g., from parents, teachers, or peers), or special talent development facilities and programs; and (c) chance (C). The DMGT includes a 5-level metric-based (MB) system to operationalize the prevalence of gifted or talented individuals, with a basic 'top 10 per cent' threshold for mild giftedness or talent, through successive 10 per cent cuts for moderate, high, exceptional and extreme levels. Complex interactions between the six components are surveyed. The text ends with a proposed answer to a fundamental question: 'What factor(s) make(s) a difference, on average, between those who emerge among the talented and those who remain average?'