so for example, i interviewed amy and named doug butler who spent decades becoming one of the best barriers and the world, that's the art of making and deploying horseshoes and finally opened his own school and is now known throughout the world and students come from all of the world. ireland, the states, saudi arabia, to study the art of it under him. and for him, learning how to teach the art of making and applying horseshoes was the ultimate extension of its own acquisition of that skill and understanding. another was alan treatment, a neurosurgeon at duke university have into it than a neurosurgeon who operated on kennedy when he and his brain tumor. here's someone who obviously doesn't have to teach, but he does. and not only does he teach his own neurosurgery residents, he teaches undergraduate that to because he's so committed to it and because for him, one of the ultimate expressions of knowing brain surgery is the ability to pass it on to others. the same was true of suki schorr, a famous ballerina who herself studied under balanchine because they knows and the ballet world and now