No chemistry textbook, classroom, lecture theatre or research laboratory is complete without a copy of the periodic table of the elements. Since the earliest days of chemistry, attempts had been made to arrange the known elements in ways that revealed similarities between them. However, it required the genius of Mendeleyev to see that arranging elements into patterns was not enough; he realised that there was a natural plan in which each element has its allotted place, and this applied not only to the known elements but to some that were still undiscovered. Today we have the so-called long form of the table. This has emerged supreme from well over 100 designs that have been proposed since the time of Mendeleyev. With the advantage of hindsight we can now see why this form of the table was bound to succeed.