Ocelli are simple, light-sensitive organs found in various animals, including some species of insects and fish. Unlike complex eyes, ocelli typically consist of a few photoreceptor cells and do not form detailed images. Instead, they help organisms detect changes in light intensity and orientation, aiding in navigation and predator avoidance. In insects, ocelli are often located on the top of the head and can complement compound eyes, providing additional sensory information. In fish, ocelli may assist in recognizing light patterns in their environment, contributing to their overall awareness and survival strategies in aquatic habitats.