铭记在心 (míng jì zài xīn) — to engrave in one's heart; to remember forever; to keep in mind always

Two or more meaningful parts placed together so that their meanings combine into a new one.

This origin belongs to the traditional form 銘; 铭 is its simplified writing.

The traditional form 銘 has 金 (metal) and 名 (name), and refers to engraving in metal; the simplified 铭 is a later shorthand.

Most characters — around four in five — are built this way: one part hints at the meaning, the other at the pronunciation.

This origin belongs to the traditional form 記; 记 is its simplified writing.

The traditional form 記 pairs 言 (speech; words) with 己 as a sound part; the simplified 记 is a later shorthand, so its right side is not the historical component.

Most characters — around four in five — are built this way: one part hints at the meaning, the other at the pronunciation.

The early form of 在 used 才 for its sound; a second sound part 士 was added later, and that 士 became the 土 seen in 在.

A drawing of the thing itself, worn down over three thousand years into a few strokes.

The shape of 心 comes from a drawing of a heart, now highly stylized.