(idiom) to be perceptive of even the finest detail; to have eyes like a hawk or see through everything

not committing the slightest offense against the people; used to describe an army or officials who are honest and strictly disciplined

The tip of a fine hair grown by birds or animals in autumn; used as a metaphor for something extremely tiny or a minute detail.

(literary) extremely precise and astute in conducting financial affairs; calculating even the smallest gains, like analyzing the fine hair of an animal in autumn

to be perceptive of the minutest detail; to describe someone with sharp vision and keen insight who understands the essence of a situation