This book develops the best traditions of this kind of scientific literature. Written by working theoretical physicists who are at the same time dedicated popularizers of scientific knowledge, the book is clear and captivating in style. It brings to the reader the latest achievements of quantum solid-state physics; but on the way it shows how the laws of physics reveal themselves even in trivial (at first sight) episodes and natural phenomena around us. And what is most important, it portrays the world through the eyes of scientists, "proving the harmony by algebra".