With the entry of Poland into the European Union in 2004, Warsaw is currently experiencing the biggest economic boom of its history. The opening match of UEFA Euro 2012 is scheduled to take place in Warsaw. (Photo by: ryarwood; Source: Flickr)

In this March 3, 2015 photo, a group of California sea lions rest on a large bouy in the San Ignacio lagoon, in the Pacific Ocean, near Guerrero Negro, in Mexico's Baja California peninsula. (Photo by Dario Lopez-Mills/AP Photo)

Savita, a street performer, helps her dog to balance on empty tin containers as they perform at a roadside in Ahmedabad September 7, 2014. (Photo by Amit Dave/Reuters)

A visitor poses with artist Joyce Pensato's artwork “Mickey for Micky” at the Frieze Art Fair in London, October 14, 2014. (Photo by Luke MacGregor/Reuters)

Ludivine Sagna walks the runway and wears a chocolate costume made by designer and a chocolate maker during the Fashion Chocolate show at Salon du Chocolat at Parc des Expositions Porte de Versailles in Paris, France, October 28, 2014. (Photo by LAURENTVU/SIPA Press)

Christian people crowd a bush taxi on a road 55km north of Bangui as they are on their way to the capital where they expect to sell some products on the market on January 19, 2014. Fresh fighting broke out in the strife-torn Central African Republic on the eve of an announcement on Sunday of the candidates seeking to become the new interim president. Sectarian violence has gripped the landlocked country after a March 2013 coup launched by the mostly Muslim Seleka rebels, and the UN has warned that the bloodshed could turn into genocide. (Photo by Eric Feferberg/AFP Photo)

A boy looks inside the skull of a Tyrannosaurus Rex replica at the Egidio Feruglio Museum in Trelew, Argentina, in this May 18, 2014 file photograph. Scientists on July 28, 2015 unveiled a comprehensive analysis of the teeth of the group of carnivorous dinosaurs called theropods, which include the Tyrannosaurus Rex, detailing a unique serrated structure that let them chomp efficiently through the flesh and bones of large prey. (Photo by Maxi Jonas/Reuters)