They have no roots, no seeds, no flowers, but mosses show immense survival capacities and can suspend their biological activity for long periods. Today, researchers are exploring the exceptional resistance of these archaic organisms. British ecologists have even resurrected a "zombie" moss that has been trapped in the permafrost for 1,500 years. Associated with decay and disliked in Europe, mosses are deified in Japan. With 25,000 species worldwide, bryophytes - their scientific name - are the seat of real ecosystems, and can develop in inhospitable landscapes, through an extravagant reproduction cycle.