In this March 18, 2015 photo, Andrea, better known as Loira, which is the Portuguese word for “blonde”, poses for a portrait in an open-air crack cocaine market, known as a “cracolandia” or crackland where users can buy crack, and smoke it in plain sight, day or night, in Rio de Janeiro, Brazil. Andrea says she is married and has a home, but she keeps returning to crackland to feed her addiction. (Photo by Felipe Dana/AP Photo)

French street artist OakOak produces creative works of art that use the characteristics of a location such as a light post, road sign and even a crack in the wall as inspiration but also as key elements in the work. (Photo by OakOak)

Traditional Hungarian horsemen pose as one of them cracks his whip over his horse in the Great Hungarian Plain in Hortobagy, Hungary June 30, 2016. (Photo by Laszlo Balogh/Reuters)

NFL player Rob Gronkowski, of the New England Patriots, from second left, accepts the best comeback athlete award with his brothers, NFL free agent Chris Gronkowski and former NFL player Dan Gronkowski at the ESPY Awards at the Microsoft Theater on Wednesday, July 15, 2015, in Los Angeles. (Photo by Chris Pizzello/Invision/AP Photo)

Derek Hough, right, and Julianne Hough, co-winners of the award fo rOutstanding Choreography for “Dancing with the Stars”, pose in the press room at the Creative Arts Emmy Awards at the Microsoft Theater on Saturday, September 12, 2015, in Los Angeles. (Photo by Chris Pizzello/Invision/AP Photo)

(L-R) Singers Kristal Lyndriette, Ashley Williams, Shyann Roberts, Brienna DeVlugt and Gabby Carreiro of June's Diary attend the 2016 BET Awards at the Microsoft Theater on June 26, 2016 in Los Angeles, California. (Photo by Frederick M. Brown/Getty Images)

Microsoft co-founder Paul Allen has spent the last six years working on a giant aircraft capable of launching rockets to space. Today, his company Stratolaunch Systems literally rolled that plane out of its hangar in the Mojave Desert for the first time ever.

Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)