In reply to the question 'what is art?' many people might tend to think of a two-dimensional surface covered in paint and enclosed by a frame. However, early cave paintings like those found at Lascaux were, needless to say, painted on the uneven face of the rock, composed out of natural resources with a creativity enhanced by various psychoactive substances and brought alive by the irregular light of a blazing torch and a far cry from the blank, bleached white canvas that is now the conventional starting point for a work of art. Although painting styled to give an illusionary effect has a much longer history, anamorphic art develops in the early Renaissance. Before the Renaissance the science of vision and the arts were two separate realms but perspective created a bridge between reality and perception. As painters began to master the principles of perspective they started to play with the rules that they were learning and developing. Anamorphosis refers to a process where an image is drawn in a distorted, often monstrous way, yet when viewed from a certain angle (direct anamorphosis) or with a particular type of reflective surface (catoptric anamorphosis), reveals to the viewer an image that they can readily recognise. As with many things, Leonardo Da Vinci was an early pioneer of this technique but one of the most famous examples of anamorphosis can be found in The Ambassadors, an oil painting by Hans Holbein the Younger currently held in the National Gallery. The painting combines a number of different artistic styles, some of which, including Trompe L'oeil, are themselves techniques creating illusionary 3-dimensional effects. The painting is replete with various symbols put there by the artist to make a wider statement about science, religion and mortality. These elements are interesting in and of themselves, but anyone familiar with the painting - it can be readily seen on their website - will know that at the bottom there is a large slither of silvery grey paint that looks almost like a smudge on an otherwise precise canvas. The purpose of this element is unfathomable until one looks upon it from an oblique angle and discovers that it is an exact representation of a human skull. Why Holbein chose to hide this skeletal form is not known and has been the subject of much speculation ever since. In the 16th century anamorphic art really took off, representatives of the Fleming school used perspective cabinets through which an otherwise unrecognisable picture would suddenly take shape - these techniques intrigued and titillated their audience. The technique was also used in architecture and columns and tunnels were designed using so-called accelerated and decelerated perspective to give the impression of false depth. The effect was to communicate illusory spaces and play with the observer's view. However the same techniques of accelerated perspective were used also, when illustrating walls and ceilings, such as those found in the Sistene Chapel, in order to create a realistic picture when viewed from the floor. The largest existing example of direct anamorphosis and a splendid early example of the technique is that found in the Convent of SS. Trinita dei Monti in Rome that is found at the top of the Spanish Steps. The single fresco (pictured) depicts two images: Saint Francesco di Paola and a landscape of the region of Calabria in Southern Italy where he lived. If you stand directly in front of the fresco, lines, insects, trees, hills, and roads, appear elongated almost to the point of being unrecognisable, forming a huge landscape reminiscent of the saint's homeland. However, if you stand at the beginning of the corridor, the image recomposes to show a depiction of St Francesco. At the time Italian artists could understand and execute anamorphic paintings, this particular version was produced using a complex set of strings, yet it was not until the 17th in France that the scientists, philosophers, mathematicians and physicists could explain its complex geometry. In today's world anamorphosis has been taken to new levels. Readers interested in contemporary examples of the technique should look out for the chalk pavement drawings of Julian Beever and the designs of István Orosz, both of whom are producing stunning work. Although neither has been quite so innovative and paradigm shaping as Hughes, in their hands that age-old role of art to educate and create wonder and awe is being kept very much alive.