The correspondence Principle. This guy which gets talked a lot has a simpler form at times. Again this principle is a specific or corollary of O = A*B with the understanding that even if one of the variable say A can be insignificant it still depends on the sequence of other variables which decides how significant the total outcome would be. Therefore given that B can be significant enough to over ride A’s insignificance the outcome O can be significant. In other words an event might correspond from a scale of insignificance to a scale of significance. Often a scale of insignificance can be the micro or nano scale and the scale of significance is reached because it is not insignificant. So there is a bridge between two scales, one of insignificance and one of significance. One of micro and one that is not micro but lies close. In all totality this is the reason why Quantum Mechanical effects can be carried to the Classical scale and this is known as correspondence Principle.