Neil Patrick Harris' daughter is getting so big!

The 43-year-old actor took to Instagram on Sunday, Oct. 30 to share that his six-year-old girl, Harper, lost her first tooth — and we couldn't be happier for her reaching this big milestone!

"Very exciting — Harper lost her first tooth! And she woke up to find that the Tooth Fairy had left a Lin-Manuel Miranda under her pillow! #Rich," Neil captioned the sweet snapshot.

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The Gone Girl star and his husband, actor and chef David Burtka, 41, welcomed Harper and her twin brother, Gideon, via surrogate in October 2010. The couple — who first publicly acknowledged their relationship in 2007 — married in Italy in September 2014.

Click through the gallery below to see more stars with twins!