眉开眼笑

méi kāi yǎn xiào

beaming with joy

Character by character

眉méi
brows

开kāi
open

眼yǎn
eyes

笑xiào
smile

收到红包，孩子们一个个眉开眼笑。

Getting their red envelopes, the kids were all beaming.

Tone: neutral.

Describes a visibly delighted face.

Learn it in context

This idiom and thousands more are in Learn Chinese with Bao, with audio, pinyin and drills that make them stick.