<http://schema.org/description>
"Twitter has begun rolling out the ability to post multiple photos as a collage from its Android app and Twitter.com. The feature lets you include up to four photos that will be displayed ..."^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/twitter/2014/05/20/twitter-begins-rolling-photo-collages-android-web/>