Three generations of gentlemen. It takes a long time to make small trees into wood. It takes more time to train a talent, which is a long-term solution and very difficult. Therefore, this sentence implies that a country, a nation and a family can succeed, multiply and inherit only by cultivating people well. As the ancients said, there are descendants from generation to generation, and the new generation changes the old. In this way, human beings can reproduce and live forever.