画龙点睛 Dotting the eyes after painting a loong

This idiom originates from the story of Zhang Sengyao (张僧繇, zhāng sēng yáo), a renowned painter during the Southern and Northern Dynasties (420 – 589). According to History of Famous Paintings Across Dynasties (历代名画记, lì dài míng huà jì), the first comprehensive history of Chinese painting, Zhang painted four golden loong, or Chinese dragons, in Anle Temple in Jinling (today's Nanjing in Jiang province). But Zhang left their eyes unpainted, claiming that giving them eyes would make the creatures fly away.

People were skeptical about Zhang's statement, so he drew in the eyes of two loongs. The beasts immediately broke free from the wall amid thunder and lightning, soaring into the sky, while the other two loongs, still eyeless, remained in place on the mural.

The tale came to symbolize the significance of a final crucial step in any literature or art creation. The idiom is now widely used to describe the practice of using a few sentences to clarify key points in writing or speeches, thereby enhancing the content's clarity and impact.

eg.

The last few sentences of the article really breathed life into the loong by dotting its eyes.

Zhè piān wén zhāng de zuì hòu jǐ jù zhēn shì huà lóng diǎn jīng zhī bǐ.

这篇文章的最后几句真是画龙点睛之笔。