Harry M. Marcowitz, William F. Sharpe and Merton M. Miller won the 1990 Nobel Prize in Economic Sciences 'for their pioneering work in the theory of financial economics'. Merton Miller contributed to the revolution of financial practice, having developed it from a loose collection of rules into a sophisticated approach to the maximization of value for shareholders. To his future followers he bestowed his studies, still unrivalled in financial economics. Franco Modigliani and Merton Miller are the authors of a theorem on capital structure, which set the new foundations for contemporary corporate finance and brought into question the generally accepted position that a firm's value depends on its capital structure, i.e. the share of equity and debt in the financing of its business operations.