Light affects mood and cognitive function. Patients with depression suffer deeply from “the blues”, with evident loss of interest and hopelessness. Fortunately, clinical trials have frequently demonstrated that light therapy can be effective for seasonal and non-seasonal major depression. In this issue, Xiaotao Li and Xiang Li discuss the therapeutic effect of light on major depression and its relationship to direct retinal projections in the brain. The cover image illustrates a patient suffering from depression who sees hope that light therapy can take him or her out of a world of darkness. The bright, warm light of this therapy enters the patient’s eyes and then reaches the depressive brain through retinal projections. See pages 359-368. (Cover art by Dr Zhirui Liu).