David Karp founded the microblogging platform Tumblr in 2007 after working at UrbanBaby, an online parenting forum. Tumblr allows users to post short messages including text, videos, and photos. It was later acquired by Yahoo! in 2013 for $1.1 billion. The document discusses different types of content on Tumblr including pornography, nature photography, humor, social justice issues, and fandoms. After the acquisition, Yahoo! implemented policies to make Tumblr more family friendly by making adult content invisible from search and tags.