Start with a single shape and repeat it in a specific way: through translation, reflection along a line, or rotation around a point. In this way, you create symmetry, a fundamental phenomenon in art, science, and nature that has been captured, described, and analyzed over the years using mathematical concepts. Inspired by Bill Thurston's geometric intuition and supported by his own analytical skills, John Conway, together with his co-authors, has developed a comprehensive mathematical theory of symmetry. This theory allows for the description and classification of symmetries in numerous geometric environments. This richly and engagingly illustrated book covers the phenomenological, analytical, and mathematical aspects of symmetry at three levels that build on each other. It is suitable for interested laypeople, artists, mathematicians, and researchers.