May 30 (Bloomberg) -- David Karp, the 26-year-old co-founder and CEO of Tumblr, started the site in 2007, at the age of 20; six years later it's the internet's preeminent blogging platform with over 300 million active users. On May 20th, Yahoo! announced that it would purchase Tumblr for $1.1 billion. Karp talks about the discussions with Yahoo CEO Marissa Mayer that lead up to the sale. TONIGHT on Charlie Rose @ 8p & 10p ET.