脑海 (nǎo hǎi): the mind; the brain

Standing on the podium, scenes of her coach's strict demands and silent dedication over the years kept appearing in her mind.

Hearing that old song late at night, happy memories of playing guitar and singing with roommates during college immediately surged into his mind.

During the exam, the answer to a difficult question suddenly flashed in his mind, and he quickly wrote it down.

Facing this complex project, a clear plan gradually formed in her mind, and she knew what to do first and what to do later.

As soon as I smelled the aroma of braised pork drifting from the kitchen, the image of Grandma busily working at the stove appeared in my mind.