心の中に

in one's heart

→ 心
phrase Rare #42,171
in one's heart Literally means “inside the heart,” but it can also refer to one's inner thoughts or feelings. Depending on context, に can indicate being in or entering someone’s heart or mind.
JA: 今でも彼女は僕の心の中にいる。
EN: Even now, she is in my heart.

もう心の中に入り込んでいる

It’s already made its way into my heart.

— 惑星ソラリス (1972)

あらゆるの歴史なりなりの心の中に始まる

The history of every country begins in the hearts and minds of its men and women.