NOT FOR POSTCARD USE Fractal geometry. A computer graphics image, entitled Dragon's Tail, showing a detail from the outer edges of the Mandelbrot Set, a group of complex numbers plotted using their real and imaginary parts as coordinates. The colour of each point depends upon its behaviour under a series of simple, but repeated, mathematical operations or mappings. The patterns are infinitely complicated, but appear to repeat themselves on whatever scale they are viewed. The study of such \chaotic\" behaviour is now used as a means of modelling real-world processes."