Everybody knows that you need light to be able to see things. But is that really true? The doctor sees the unborn baby by using ultrasound. And in a slightly different way so does the bat. The air traffic controller sees the oncoming plane by using radar. Soldiers use heat wave to see the hidden enemy. Then of course the artist sees by using his imagination. And there are more examples: the scanning microscope uses electrons to see very small animals, etc.So, seeing with light is just one way of perceiving the world around you. The images in this book are made by using x-rays (the x-rays for finding broken bones). And you will see that x-rays help you see the world in another light.