Volunteers of the first group and the second group wave in the cabin at Beihang University in Beijing, Jan. 26, 2018. Two male and two female students from Beihang University, the second group of volunteers staying in Yuegong-1, also known as Lunar Palace 1, completed the second phase of its 365-day on-ground experiment Friday, setting a world record for the longest stay in a self-contained "cabin." The first group of volunteers, who had previously stayed in the cabin for 60 days, re-entered the cabin to replace the second group, starting the third and final phase which will last 105 days. The experiment was designed to see how the Bioregenerative Life Support System (BLSS), in which animals, plants and microorganisms co-exist, works in a lunar environment, as well as the physical and mental conditions of humans in such an environment. (Xinhua/Luo Xiangguang)