The paper traces the history of Human Capital from the earliest definitions of classical economists and the Retrospective and Prospective estimation methods . Its conception is gradually refined by giving reasons for personal and collective variability among different individuals. The Chicago School's introduction of the link between the investment in Education and Training and their remuneration represents an early milestone in this regard. Reference to the Quality of Education and personal Cognitive Skills further refines the theoretical and quantitative analysis. More recently, Heckman's introduction of the concept of Non cognitive Skills and the demonstration of their functional, empirically verifiable link with Cognitive Skills opens a new horizon of enormous scope to research.