A man presents a self-made robot that local media reported is able to carry a person, in Heihe, Heilongjiang province, China, April 5, 2017. (Photo by Reuters/China Daily)

Two men fight in San Jose, Costa Rica, during the Women's Day on March 8, 2014. (Photo by Jeffrey Arguedas/EFE/SIPA Press)

Hotel staff practice self-defence skills after a training session given by team member of Special Weapons and Tactics (SWAT) team, in Hangzhou, Zhejiang province, April 7, 2016. (Photo by Reuters/Stringer)

A Palestinian beekeeper uses smoke to calm bees in the process of collecting honey at a farm in Rafah, in the southern Gaza Strip April 11, 2016. Rateb Samour sees 250 patients a day, whose complaints range from hair loss to cerebral palsy and cancer. He is not a doctor and has never worked in a hospital. Samour inherited the skill of bee-sting therapy from his father. From 2003 the agricultural engineer dedicated all his time to study and develop the alternative-medicine treatment of apitherapy, which uses bee-related products from honey, propolis – or bee glue used to build hives – to venom. (Photo by Suhaib Salem/Reuters)

People play on a beach along the Arabian Sea on a hot summer day in Mumbai, India, April 29, 2016. (Photo by Danish Siddiqui/Reuters)

Women look on as Sauber's German driver Pascal Wehrlein steers his car during the second practice session at the Monaco street circuit on May 25, 2017 in Monaco, three days ahead of the Monaco Formula 1 Grand Prix. (Photo by Andrej Isakovic/AFP Photo)

Men slide in the mud during the Boryeong Mud Festival at Daecheon Beach in Boryeong, South Korea, Saturday, July 22, 2017. The 20th annual mud festival features mud wrestling and mud sliding. (Photo by Ahn Young-joon/AP Photo)

Green algae sits on a beach in Kuwait City, Kuwait, 28 February 2017. The formation of green algae is a normal phenomenon that occurs every year at the shores of Kuwait. (Photo by Raed Qutena/EPA)