Zolciak, now 38, was only 18 years old when she gave birth to Biermann, and needless to say, she can't believe how fast her daughter has grown.
"Happy Birthday to my angel @briellebiermann I just can't believe it!!!," the mother of six wrote. "I just can't believe it was 20 years ago today I became your mom! Scared out of my mind yet so excited! Had I known how easy it would have been to raise you I certainly would of had a lot less anxiety!"
"I'm extremely proud of the leader you are, the heart you have and share, the love you have for your siblings, the respect, loyalty, and commitment to your family and above it all how you always have remained TRUE to you!! Keep shining!!! Can't wait to squeeze you!! Love you oh so much!!!," she concluded. "#HappyBirthdayBrielle #TheBig20 ??????."