The Obamas' youngest daughter just turned 20.

Today marks Sasha Obama's 20th birthday and to celebrate, former first lady Michelle Obama shared a sweet snapshot of her daughter. Appropriate for a Throwback Thursday, the photo is a never-before-seen image of the mom-and-daughter duo on a boat together. Sasha, the Obamas' youngest daughter, is wearing a life vest and navy shorts while her mom is in a coordinating blue top and white pants.

"Happy birthday to my darling Sasha! I am so grateful for every laugh we've shared - and everything you've taught me over the years," Obama wrote on Twitter. "You'll always be my little girl, but I couldn't be prouder of the woman you are becoming. Love you so much!"

Sasha's father, former President Barack Obama, also posted a tribute to his daughter - of course, his message was a throwback, too. In his photo, he's carrying Sasha and both of them have huge smiles.

"Happy birthday, Sasha! You've grown so much, and it's been a joy to watch you become the person we always hoped you'd be," he wrote on Instagram. "Your mom and I can't wait to see where life takes you next."