What is symmetry and what do we call symmetrical?  For most people, the concept of symmetry is limited to mirror, or axial symmetry.  However, this is only a special case of true symmetry.  The purpose of this book is to tell about the variety of types of symmetry that exist in the world.  For example, radiolarians, diatoms and viruses have external symmetry, crystals have internal symmetry, and even the Universe itself has various types of quantum symmetry, which has long been known to physicists.  Let's open the gates to the kingdom of symmetry!