Through billions of years of evolution, nature has created biological materials with remarkable properties. Studying these biological materials can guide the design and fabrication of bio-inspired materials. Many of the complex natural architectures, such as shells, bones, and honeycombs, have been studied to imitate the design and fabrication of materials with improved hardness and stiffness. Recently, an increasing number of researchers have investigated the wings of lepidopterans (butterflies and moths) because these structures may exhibit dazzling colors. Based on previous studies, these iridescent colors are attributable to periodic structures on the scales that constitute the wing surfaces. These complex and diverse structures have recently become a focus of multidisciplinary research due to their promising applications in the display of structural colors, advanced sensors, and solar cells. This review provides a broad overview of the research into these wings, particularly the microstructures in the wing scales. This review investigates the following three fields: structural characterization and optical property analysis of lepidopteran wings, modeling and simulation of the optical properties and microstructure, and the fabrication of artificial structures inspired by these wings. (C) 2014 Elsevier Ltd. All rights reserved.