〜最中（に）
Right in the middle of… when (at the peak)machine translation
FormationVerb ている-form + 最中（に）／noun + の + 最中（に）
〜最中に (read さいちゅう) expresses "right in the middle of an action at its liveliest, something happens": 会議の最中に携帯が鳴った (right in the middle of the meeting, a cell phone rang). The event in the second clause is usually unexpected, causing an interruption or an awkward moment.
Connection: verbs use the ている-form (考えている最中に), and nouns denoting activities connect with の (食事の最中に, 試合の最中に). At the end of a sentence you can say 〜最中だ: 今、調べている最中です (I'm right in the middle of looking it up).
Compared with 〜あいだに (N4), which marks a time span neutrally, 最中に stresses "at the very peak, right in the middle of it," so it doesn't suit static, long-lasting states. Compared with 〜ているところに, the two patterns are quite close; 最中に carries a stronger flavor of "a high point being cut short," and only 最中 can connect directly to a noun.
Examples
会議の最中に、携帯電話が鳴ってしまいました。
Right in the middle of the meeting, my cell phone went off.
試合の最中に雨が降り出した。
Right in the middle of the match, it started to rain.
考えている最中ですから、少し静かにしてください。
I'm in the middle of thinking, so please be a little quieter.