Wang Xi-zhi is one of the most famous calligraphers(书法家) during the Eastern Jin Dynasty of China. When he was very young, he practiced his art every day and never stopped.
Later he absorbed the strong points of all the other schools of calligraphy1, and developed his own unique style of writing. Because of his achievements, he has been honored as one of China's sages2 of calligraphy. One time, Wang Xi-zhi sketched3 in wood for an engraver4 to cut. Then the engraver found the ink had penetrated5 one centimeter into the wood.
"Ru Mu San Fen6" is got from this story, which means the calligraphy is penetrating7.
Now it is often used to describe expressing sharp ideas or profound views.