This document summarizes the development of management thought across three stages: classical theory, neo-classical theory, and modern management theories. The classical theory included bureaucratic, scientific, and administrative management approaches. The neo-classical theory focused on the human relations movement and behavioral sciences movement. Modern management theories include the systems approach and contingency approach. Key thinkers discussed include Weber, Taylor, Fayol, Mayo, Maslow, McGregor, and others. The document outlines the principles and contributions of these various approaches to management thought over time.