Copper (Cu) is an essential component of biological redox reactions and its deficiency is fatal to the body. At the same time, Cu is extremely toxic when present in excess. In this regard, several groups of Cu-regulating proteins in the body act to regulate the concentration of Cu within a certain range. However, the overall mechanism underlying the maintenance of Cu homeostasis in the body and cells remains poorly understood. In this review, recent research tools, such as animal models and gene-modified animals, and techniques, such as speciation and imaging of Cu, are highlighted.