Nicolas Jaeger, born in 1946 in Boulogne-Billancourt and died in 1980 in Lhotse, is a French doctor and mountaineer. He is the author of more than a hundred solo ascents in the Mont-Blanc massif and in the Andes, including many “first solos”. On October 15, 1978, he was one of the first French people to reach the summit of Everest, with Pierre Mazeaud and Jean Afanassieff accompanied by the Austrian Kurt Diemberger, altitude cameraman. Son of photographer Janine Niépce and film producer Claude Jaeger, Nicolas Jaeger was born on October 20, 1946 in Boulogne-Billancourt. He was very close to his grandfather Niepce, one of the pioneers of aviation, co-founder of the Construction of flying machines and spare parts company, with whom he learned whole passages from the Adventures of Tintin albums by heart, developing according to his mother his vocation as an adventurer. He studied medicine and practiced mountaineering: he became a doctor and in 1975 graduated from his promotion as a mountain guide. In 1977, Nicolas Jaeger was the leader of an expedition to Peru during which he opened new routes alone on several peaks over 6,000 meters. He returned to Peru in 1978 for an ultra-light expedition which again allowed him to make his first solo ascents. The same year, Nicolas Jaeger participated in the first ascent of Everest by a French expedition led by Pierre Mazeaud, with Jean Afanassieff and Kurt Diemberger. He reached the summit on October 15 with Afanassieff and they were the first to descend an 8,000-meter peak on skis. This heavy expedition, with its many porters, oxygen cylinders, altitude camps, does not correspond to the style of mountaineering practiced by Nicolas Jaeger, a light mountaineering, often alone. But this expedition is an opportunity for him to climb Everest (a mountain still rarely climbed at the time), to benefit from a media exposure which will facilitate his future projects and to observe the behavior of the human body at high altitude. . The following year, he went to live alone from July 27 to September 27, 1979 at an altitude of 6,700 meters in Peru, under the summit of Huascarán, to study human physiology at high altitude on his own. He is looking for “a kind of super-acclimatization” made possible by prolonged stays at altitude. He writes a daily diary of his stay, the Carnets de solitude, which he will publish on his return. Not having suffered from altitude sickness during this long stay, he noticed his great ability to acclimatize to altitude. With his experience of altitude and solo mountaineering, he returned to the Himalayas in 1980 with the goal of climbing the south face of Lhotse, alone, without oxygen, without the help of porters. On April 28, 1980, Jaeger disappeared after being last seen nearly 8,200 meters above sea level on the south face of Lhotse. He was married and the father of two daughters.