Credit: Barry King/FilmMagic

He's the boss of her heart!

Alyssa Milano and husband David Bugliari officially became parents on Tuesday morning, welcoming son Milo Thomas.

And the New Year's Eve actress, 38, re-emerged on her beloved Twitter after the big news hit to proclaim her gratitude -- and her joy.

"Thank you for all the well wishes for my son Milo," Milano wrote. "My heart has tripled in size. I love him more than all the leaves on all the trees."

An insider tells Us Weekly Milano was in labor for 12 hours before Milo arrived at 9:27 a.m., weighing 7 pounds and measuring 19 inches long.

It's the first child for Milano and agent Bugliari, who wed in August 2009.

The couple hosted a baseball-themed baby shower Aug. 14 at L.A.'s Dodger Stadium with such boldfaced attendees as Holly Robinson Peete, Colin Hanks and Twitter founder Jack Dorsey.