 Lipases are important industrial enzymes used in various applications such as food processing, detergent manufacturing, and biofuel production. The majority of lipases operate at lipid water interfaces where they are stabilized by a mobile lid domain. This lid domain is composed of one or more helical structures which open or close depending on the presence of a hydrophobic layer. Thermostable lipases typically possess large lid domains with multiple helices, while mesophilic lipases have small lid domains consisting of loops or helices. Recently, advances in lipase engineering have focused on modifying the lid region to improve activity, substrate selectivity, and thermostability. Computational models have also been developed to explain how lid mobility affects lipase function. This article was authored by Faiz Iqbal Khan, Dong Ming-Lan, and others.