Buffett taught his children to be rational when investing, and if you can't understand it, don't do it, do what you fully understand. He always insists on the investment principle of "business is not familiar and not done", and always only puts his eyes on the field in which he is sure. It is not difficult to find that his lock stocks are basically concentrated in finance, consumer goods, media and other familiar fields in daily life, he always consciously stay away from those inves...