Workers prepare the roof of a house to get installed solar power modules for producing heat on October 15, 2011 in Wessling, Germany. Germany has and is continuing to invest heavily in solar energy, both in the public and private sectors. The German government introduced a feed-in tariff with its Renewable Energy Act in 2000 that guarantees homeowners a minimum rate for selling electricity from renewable energy sources into the nation's electricity grid. (Photo by Alexandra Beier/Getty Images)

Dai Shuqing's husband sits among adopted stray dogs at an animal shelter on December 15, 2006 in the outskirts of Xian of Shaanxi Province, China. The animal shelter, established by animal lover Dai Shuqing, is located at an abandoned warehouse which houses some 100 dogs and costs over 2,000 yuan (about US $255) per month. (Photo by China Photos/Getty Images)

A girl poses at an entrance of her house next to a bomb dropped by the U.S. Air Force planes during the Vietnam War, in the village of Ban Napia in Xieng Khouang province, Laos September 3, 2016. From 1964 to 1973, U.S. warplanes dropped more than 270 million cluster munitions on Laos, one-third of which did not explode, according to the Lao National Regulatory Authority. (Photo by Jorge Silva/Reuters)

An arrow-head discovered in 2006 by Archaeologists of the University of Cambridge Archaeological Unit, is displayed by one of the team uncovering Bronze Age wooden houses, preserved in silt, from a quarry near Peterborough, Britain, January 12, 2016. Archaeologists said on Tuesday they had discovered what were believed to be the best-preserved Bronze Age dwellings ever found in Britain, providing an extraordinary insight into prehistoric life from 3,000 years ago. (Photo by Peter Nicholls/Reuters)

An Afghan boy plays in the ruins of a house that at one point belonged to the 13th-century Persian poet, Islamic scholar and Sufi mystic Jalal ad-Din Muhammad Rumi on the outskirts of Mazar-i-Sharif on November 25, 2015. (Photo by Farshad Usyan/AFP Photo)

A model presents a creation by Bulgarian designers Livia Stoianova and Yassen Samouilov as part of their Haute Couture Spring/Summer 2016 fashion show for fashion house On Aura Tout Vu in Paris January 25, 2016. (Photo by Gonzalo Fuentes/Reuters)

A man looks at a mural painted on the walls of houses in Zaraeeb, created by French-Tunisian artist El Seed, in the shanty area known also as Zabaleen or “Garbage City” on the Mokattam Hills in eastern Cairo, Egypt, April 4, 2016. (Photo by Amr Abdallah Dalsh/Reuters)

Brazilian top model Gisele Bundchen poses before a fashion show by German designer Karl Lagerfeld as part of his latest inter-seasonal Cruise collection for fashion house Chanel at the Paseo del Prado street in Havana, Cuba, May 3, 2016. (Photo by Alexandre Meneghini/Reuters)