Pierre Cammalletti, technical director for the controlled Mycorrhization program looks with a microscope at the spores of tuber magnatum implanted on a truffle oak on February 25, 2021 in the laboratory of Robin's nursery in Saint-Laurent-du-Cros near Gap, southeastern France. - After more than 20 years of research, a nursery in the Hautes-Alpes has succeeded in control the cycle of white truffles, which are as expensive as they are difficult to produce. (Photo by Philippe DESMAZES / AFP)