Obama posted the love note to the former first lady on her 55th birthday, along with a throwback photo of the couple.  

“I knew it way back then and I’m absolutely convinced of it today — you’re one of a kind, @MichelleObama,” he wrote. “Happy Birthday!” 

People on Twitter responded by adding their birthday wishes for the bestselling author. 

“Happy Birthday to The Best FLOTUS we’ve ever had!!!” one person wrote on Twitter. 

“Happy Birthday Michelle! I loved your book and I love the both of you even more now!” another added. 

Since leaving the White House, Michelle Obama has embarked on a nationwide book tour for her bestselling memoir, Becoming.

Penguin Random House said in November that the memoir sold more copies than any other book published in the U.S. in 2018. Amazon this week said  Becoming had the longest streak at No.1 for any book, surpassing Fifty Shades of Grey’s run after it came out in 2012, CNN reported.