light up

To illuminate, to bring light to something, to brighten.

To show an increase in activity or a brightening of mood.

"He saw Mary and his face lit up."

To light a cigarette, pipe etc.

"Smoking in this building is not allowed, so I always step outside to light up."

To make happy.

To loosen, slacken or ease off.

"to light up the jib-sheets"