Thinking about the French Flag and how it could possibly work, one way would be that there would be some molecule made at one end and it would diffuse to the other end and it would set up a gradient in this... there would be a gradient, a graded set of concentrations along the flag. Gradients had been around... for quite a long time and, in fact, there’s one particular concept that goes back to Alan Turing who spoke about morphogens and that is, once again, diffusible molecules that may be involved in... in pattern formation. And the real problem was, how could this gradient be set up and what would it be a gradient in and how would the cells really interpret it? But the key point with the French Flag Model was the concept of positional information, that is, that cells would have a positional identity and that would determine how they behaved.