You cannot be sure in advance exactly how the situation, the scene, is going to unfold. You must stay with the scene, just in case the elements of the situation shoot off from the core again... Of all the means of expression, photography is the only one that fixes forever the precise and transitory instant. We photographers deal in things which are continually vanishing, and when they have vanished, there is no contrivance on earth which can make them come back again. We cannot develop and print a memory.