Chloroplasts relocate their positions in a cell in response to the intensity of incident Light, moving to the side wall of the cell to avoid strong Light, but gathering at the front face under weak Light to maximize Light interception. Here, Arabidopsis thaliana mutants defective in the avoidance response were isolated, and the mutated gene was identified as NPL1 (NPH-Like 1), a homolog of NPH1 (nonphototropic hypocotyl 1), a blue Light receptor used in phototropism. Hence, NPL1 is Likely a blue Light receptor regulating the avoidance response under strong light.