Euclid is considered the father of geometry. He lived in Alexandria during the reign of Ptolemy I and must have flourished about 300 BC. His central work was the Elements, where he presented the fundamental concepts and principles of geometry and, based on five indemonstrable postulates or axioms (e.g. two points determine one and only one straight line), managed to summarise the geometric wisdom of the time in a comprehensible and coherent system, named Euclidean geometry in his honour. His influence was so immense that it was not until the 19th century that a non-Euclidean geometry was developed. He also wrote Optics, Catoptrics, Conics, etc. They say that when Ptolemy once asked him if there was in geometry any shorter way than that of the Elements, he replied that there was no royal road to geometry.