Old snow? For the scientists, the condition of glaciers is one of the most important indicator of climate changes. In the valley of Chamonix and in the mountain massif of the Mont Blanc, the pioneers of the climate and glacier research gathered their knowledge at the end of the 19th century and thus gave birth to the sciences of mountains. This documentary follows the footsteps of a climate and glacier scientist through the impressive mountain world and demonstrates how glaciers are born and how they react when the climate changes. Exploring these mechanisms, many of these scientists have risked their lives.