Atmosphere water harvest offers a creative and straightforward way to tackle the global-range freshwater shortage, especially in remote areas and arid deserts. Inspired by the natural species, significant progress has been made to developing water harvesting materials and devices through the rational design of the structure and composition. In this review, we address mainly three questions. What is the design principle of a water harvesting material? How to improve the water collection efficiency of a material in an arid region? How to transform the materials into high-efficient water harvesting systems/devices? With these questions, we present a systematic interpretation of in-air water harvesting, from the materials to the devices, aiming to help find ever-advanced water harvesting systems. We summarize the important achievements towards their applications in the sustainable water supply at water-deficient regions, and for the agricultural irrigation system. The challenges and barriers that retard their applications and future research orientations in this field are also discussed.