Phototropism is a biological phenomenon in which plants, animals, and other organisms move or orient themselves in response to directional stimulus from light. Plants, for example, can grow towards or away from a source of light, or a combination of the two. In animals, phototropism is a response used for navigation, growth, and development. The movement could be gradual and continuous, or instantaneous, such as certain reflexes in insects. In addition, the response is often directional, meaning the organism shows a preference to orient in the light or away from it.