This document discusses the evolution of organizational design over three eras and various forms of organizational structure. It outlines key developments in organizational structure and design that have led to greater effectiveness. These include moving from self-contained organizations to horizontal and modular/virtual structures. The document also outlines different design rules for various organizational structures, such as functional, divisional, and matrix designs. It discusses how organizations have moved to outsourcing non-core processes and forming temporary partnerships to pursue market opportunities. The objective is to present optimal organizational designs and structures for different contexts.