However, we've recently learned trees can actually sense the world around them, and if they're attacked, they can fight back in their own way. And they do this by using the same senses that we have. Well, some of them anyway. So let's start with sight, which is based on sensing light. Trees do not have eyes, but they can sense and grow towards the light, and light is what they need to create food through photosynthesis. So, this means that they can tell day from night, and they'll behave differently according to the time of day, a bit like we do. They can sense the ambient light using various chemicals, and can even tell the difference between bluish light and reddish light. And so, by detecting what wave lengths of light are landing on their leaves, trees know if they're in the shade of a building, or of another tree.