Gwyneth Paltrow and Chris Martins son is officially an adult (and doesnt that make you feel old?).

Paltrow posted an emotional birthday tribute to her youngest kid, Moses, on Monday, in honor of his 18th birthday.

I am so proud of who you are. I love your sensitivity and brilliance and quiet humor, she wrote. There is such a magnificent world of ideas and harmonies inside that beautiful head of yours.

I am unbelievably proud of the person you are today, as you cross over the threshold into adulthood. I love you more than words can say, @mosesmartin you absolutely kill me, the actor wrote, before signing off with Mama.

While Paltrows celebrity friends Kate Hudson and Reese Witherspoon shared their birthday wishes for Moses in the comments, most fans couldnt get over just how much he looks like his famous father.