聚精会神 (jù jīng huì shén): to concentrate one's attention (idiom)

He always concentrates fully when doing homework, unaffected by outside distractions.

Please listen to the teacher's explanation of the text with full attention.

She was so absorbed in drawing that she didn't hear her mother calling her to dinner.

In the library, everyone is reading with complete concentration.

The scientist concentrated deeply on the difficult problem and finally found a solution.