This article reviews the fundamental properties, foam-ing mechanisms, and processing technologies for PLAfoams. First, we address fundamental studies made ofPLA/gas mixtures, which are required for the foaming ofPLA. We discuss the development of PLA foams throughvarious mechanisms, and examine the efforts that havebeen made to achieve low-density microcellular andnanocellular PLA foams. The article also introduces themanufacturing technologies that have been applied in PLAfoam production.