Kris Jenner can't believe how fast Kylie Jenner has grown up.

The 'Keeping Up With The Kardashians' star was thrilled to be celebrating her youngest daughter's 21st birthday and quipped that it feels like it's been ''one minute'' since she gave birth to her.

Taking to the microphone at Kylie's party, Kris said: ''I've loved watching her grow up every birthday and give birth to baby Stormi ... We're all celebrating Kylie ... 21 years ago almost seems like one minute ago today, I gave birth to Kylie.''

And Kylie feels a similar sentiment as she previously confessed she can't believe how quickly her baby daughter Stormi is growing as she got sentimental on Twitter to reflect on the changes that the tot has already gone through.

She tweeted: ''Stormi will be 6 months in 6 days ... how did this happen? Moms, do your babies grow as fast as mine?''

The brunette beauty has ''blossomed and matured'' since becoming a mother, according to her best friend Jordyn Woods.

She said: ''I think just people grow and evolve every day and when you become a parent you have to keep learning and it's an experience and I have just seen her blossom and mature, so it's nice. It's just how any relationship would be, you have experiences together.''

And Kris feels incredibly ''proud'' of Kylie Jenner's business success.

Alongside a picture of Kylie on the front of Forbes magazine, she wrote: ''My beauty on the cover of Forbes Magazine!! I am SO proud of you @kyliejenner and everything you have accomplished. You work so tirelessly on your business, and with so much passion and precision. As a mother, it brings me immense joy to watch you continue to make your @kyliecosmetics dreams a reality!! @forbes #Forbes [sic]''