Used when examining, explaining, or investigating something thoroughly, paying attention to fine points. Often appears in formal or written contexts.
We need to investigate the circumstances of the incident in detail.
He examined the contract minutely.
Standard kanji spelling for the adverbial form.
Alternate kanji spelling; 子細 is a variant of 仔細.
From the noun 仔細 (しさい, 'details; circumstances') combined with the adverbial particle に. The kanji 仔 and 細 both relate to smallness or fineness, reflecting the sense of minute examination.