The brains of human beings at rest are supposed to use a fifth of the energy produced by their bodies, i.e., about 20 W of power. In fact, the cost would be much more if our brains were not equipped with an efficient coding mechanism that allows us to represent only the information which is really useful in the vast, ongoing stream of sensory stimuli. A new study conducted by SISSA and the University of Pennsylvania, published in eLife, shows the existence of similar efficient coding processes for visual stimuli in rodents. The results add support to the important efficient coding theory of sensory perception, and pave the way towards new experimental approaches for understanding underlying neuronal mechanisms and the development of new training protocols for artificial vision systems.