This document summarizes the evolution of environmental control systems used in greenhouses, current systems, and future systems. It discusses how temperature, humidity, lighting, photoperiod, atmospheric composition, irrigation, and nutrient delivery can be regulated. It outlines the types of controls that have been used, including manual controls, on/off switches, step controllers, dedicated microprocessors, and computers/integrated control systems. It provides examples of early manual greenhouse controls and describes the functionality of on/off switches, step controllers, dedicated microprocessors, and integrated computer control systems.