The time when the sky begins to grow light; often used poetically or in news contexts.
Let's leave before dawn.
The sky at dawn was beautiful.
The climbers greeted the dawn at the summit.
The birds began to sing as dawn broke.
She left before dawn.
This is the dawn of a new era.
夜明け emphasizes the moment day breaks and light appears, whereas 未明 focuses on the still-dark hours just before that happens.
夜更け is the deep, late part of the night, while 夜明け is dawn, when night ends and day begins.