A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

A young exhibitor arrives with her kitten on a lead at the National Cat Club show at Crystal Palace, London. (Photo by Fox Photos/Getty Images). 2nd December 1931

Psychotria is a genus containing some 1900 species within the plant family Rubiaceae. Members of the genus are small understorey trees in tropical forests. The former genus Cephaelis is considered a synomym of Psychotria.

Krastsvetmet, located beside the beautiful Yensei river in the metropolis of Krasnoyarsk, Russia, is a refinery of all types of precious metals on an industrial scale.

Just a week before Rio de Janeiro hosts South America's first Olympics, city residents expressed mixed feelings about the cost and security of the Games, while holding out hope they will bring joy to a nation facing economic and political crises. The conflicted thoughts mirror a recent survey by the Datafolha polling group showing that half of Brazilians were opposed to holding the Games, while 63 percent think the costs of hosting the event will outweigh benefits. (Photo by Pilar Olivares/Reuters)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

Indigenous dancers participate in a traditional healing ceremony for the mother earth at El Salvador del Mundo Square in San Salvador, December 10, 2014. Salvadorean indigenous organizations participated in a ceremony to ask for solutions to stop climate change and respect planet earth as the U.N. Climate Change Conference COP 20 is bring held in Peru. The two-week long United Nations climate summit opened on December 1 in Lima, with experts and analysts from around the world gathering to discuss melting glaciers and extreme weather patterns. (Photo by Jose Cabezas/Reuters)