A group of youngsters dressed as ghouls and zombies for Halloween parade in downtown Lisbon, Portugal, Friday, October 31, 2014. (Photo by Francisco Seco/AP Photo)

A tunnel with electric switches are seen in Josip Broz Tito's underground secret bunker (ARK) in Konjic, October 16, 2014. In the early 1950s, Josip Broz Tito, the late leader of the former Yugoslavia, ordered the building of the secret bunker, located 900 feet (270 m) underground and near the Bosnian town of Konjic, to safeguard the country's ruling class in case of a nuclear attack. Construction at the complex, which had a cost equivalent price tag of $4.6 billion, continued until 1979, the year before Tito died. (Photo by Dado Ruvic/Reuters)

Mr. Zhong Hua, of Johns Hopkins University School of Medicine, took this image of the peripheral nerves (those outside of the brain) in an 11.5-day-old mouse embryo, magnified five times. (Photo by Zhong Hua)

Local villagers fall onto the ground from an ox-cart as they ride to rid evil spirits from their village at Pring Ka-ek village, Cambodi. (Photo by Heng Sinith/AP Photo)

“The Net thrower”. The fisherman are conducting activities on Situgunung Lake. Photo location: Situgunung lake, Sukabumi, West Java, Indonesia. (Photo and caption by Dody Kusuma/National Geographic Photo Contest)

Female sea lion “Sarasa” holds a hose with her mouse to help a trainer clean her room at the Shinagawa Aqua Stadium aquarium in Tokyo on December 30, 2014. The aquarium is carrying out year-end general cleaning of their facilities. (Photo by Yoshikazu Tsuno/AFP Photo)

An Indian toddler plays amid marigold flowers at a wasted flowers dumping site, besides a flower market in Mumbai, India, 28 September 2016. Marigold flowers are used in many religious ceremonies in the temples in India. Strung together they make colourful garlands and are used as an offering in temples and to decorate them. (Photo by Divyakant Solanki/EPA)

The sea otter mother with her three day old newborn pup ontop of her to keep it dry and warm while it sleeps. This devoted mother otter kept her newborn pup dry as she let the baby ride on her belly. Nature photographer Suzi Eszterhas, 40, spotted the adorable pair of southern sea otters swimming in Monterey Bay, California. The mother lifted the pup out of the water and on to her belly to keep it warm and dry and also blew air into the pup's fur to groom it. Ms Eszterhas was shocked to see the otters come closer to where she was standing and the mother left her child to float alone in the water. (Photo by Suzi Eszterhas/Minden Pictures/Solent News & Photo Agency)