Madonna is Will Sage Astorgetting into the groove for a special occasion.

The "Material Girl" singer penned a sweet birthday message in honor of daughter Mercy's 18th birthday.

"You're already a young woman," Madonna wrote alongside a montage of photos Instagram Jan. 22. "Beautiful African Queen!! You Surprised all of us! You were always the quiet one. The gentle one. The Shy and Stoic one."

In the heartwarming video, Mercy, who Madonna noted is "always humble and kind," is seen showcasing her talents such as playing the piano, as well as posing in pics with her mom and siblings.

"I am really astounded by the woman you have become," Madonna continued. "Poised and radiant. Skilled and Soulful. A True artist."

In fact, the Grammy winner—who is also mother to Lourdes, 27, Rocco, 23, David, 17, and twins Estere and Stella, 11—remains inspired by her artistry.

"That hand that was once frozen in your mouth as a child-now makes magic happen when you play the piano," Madonna reflected. "To hear you play Chopin every night in my show with such confidence is such a thrill."

But the "Vogue" singer didn't just praise her daughter's skills, as she also detailed how Mercy has grown over the years.

"To watch how you care for your younger sisters," she noted. "To see you unfold from A Chrysalis to a Butterfly. Beautiful Chifundo James. Nothing gives me greater pleasure than to watch you grow. You really are A wonder."

Madonna concluded her touching tribute with a note about the future.

"The happiest of everything— because you deserve it," she added. "Even though we both hate shellfish the world is your Oyster !! She is waiting for you to devour it. To eat it whole!!! To Slay it!!"

For the latest breaking news updates, click here to download the E! News App