Photosynthetic organisms are crucial for life on Earth as they provide food and oxygen and are at the basis of most energy resources. They have a large variety of light-harvesting strategies that allow them to live nearly everywhere where sunlight can penetrate. They have adapted their pigmentation to the spectral composition of light in their habitat, they acclimate to slowly varying light intensities and they rapidly respond to fast changes in light quality and quantity. This is particularly important for oxygen-producing organisms because an overdose of light in combination with oxygen can be lethal. Rapid progress is being made in understanding how different organisms maximize light harvesting and minimize deleterious effects. Here we summarize the latest findings and explain the main design principles used in nature. The available knowledge can be used for optimizing light harvesting in both natural and artificial photosynthesis to improve light-driven production processes.