画龙点睛

huàlóng-diǎnjīng

[add the touch that brings a work of art to life; add a word or two to clinch the point; put life into sth.like dotting the eyeball in painting a dragon] 以唐·张彦远《历代名画记》所述张繇僧画龙点睛的故事, 比喻绘画、 作文在紧要之处加上一笔, 使其灵活而有神