Injection molding is one of the most popular polymer processing methods and has been used to mass produce plastics products for many decades. However, due to increasingly stringent requirements and higher customer expectations, conventional injection molding cannot always meet all manufacturing specifications. Hence, many advanced injection molding technologies have been developed to accommodate the higher standards and special features. Those technologies include the following: • Multi-component molding techniques such as over-molding, insert molding, co-injection molding, and bi-injection molding. • Lightweight technologies such as injection molding using fiber-reinforced plastic (FRP), microcellular injection molding, gas-assisted injection molding, and water-assisted injection molding. • Advanced heating and cooling management techniques including advanced hot runner systems, conformal cooling, and variotherm technologies. • Special molding technologies such as injection–compression molding, compression molding, and so on.