Although light is the source of energy for photosynthesis, it can also be harmful to plants. Light as a stressor induces damages which target mainly the photosystem II. Inactivation of electron transport and subsequent oxidative damage of the reaction center may occur. However, light is able to activate special adaptation mechanisms in such a way that the efficiency of the photosynthetic system is optimized and the photodamage is minimized. In the review, different constructive and destructive aspects of light stress are discussed in aquatic and land plants. The response and adaptation of photosynthetic machinery of plants to high light and different environmental perturbations are summarized. In addition, recent advances in understanding the biochemical changes in response to light have been discussed. Different ecophysiological and biochemical protective mechanisms against light stress have also been described.