Barack and Michelle Obama are celebrating their 25th wedding anniversary today, and the former First Lady paid tribute to their milestone in a sweet way. The health and education advocate shared a throwback photo from her and the former president's wedding day, with a heartfelt note. "Happy 25th anniversary," she tweeted. "A quarter of a century later, you're still my best friend & the most extraordinary man I know. I 💕 you."The former Commander-in-Chief is probably formulating an equally romantic and tear-jerking response.