Blue is a rare color. You may look up at the sky in protest, but if you submit your environment to closer scrutiny, you will soon realize that blue occurs very rarely among animals and plants. Since their beginnings, humans have been searching for uniquely blue stones and dyes to transform fabric, porcelain, or paintings. Blue has always had a fascinating quality, as is shown in the authors’ quest for a blue flower or the magical blue of a bird’s feather coat. Kai Kupferschmidt succumbed to this fascination as a child, and it has stayed with him ever since. His investigation into the mysteries of this color led him to Japan, a volcanic lake in Oregon, and on to the last few Spix’s macaws in Brandenburg, Germany. Rocks, plants, animals, or the distant view of our planet from the depths of space, they all bear witness to an overwhelming beauty that is reflected in our language and the written word. And it all starts with light and our ability to see.