You have never heard of this moss. That is the point. It was tiny – so tiny that you could press your face against the cliff and still not see it. Its stems were the height of a grain of rice, its leaves were smaller than a pinhead, its entire being was compressed into a few square millimetres of rock crevice. It was the hidden phantom of the cliff, a living speck in the stone. Smallness and secrecy made it special. The tiny mossy crevice was a specialist of the narrowest cracks – the deepest fissures, the darkest crevices, the places where water trickled and light never reached. It needed nothing but a crack, a bit of moisture, and the patience to grow for decades. It was the minimalist of the moss world. The stems were short and dark, with tiny, scale-like leaves pressed tightly against them. The colour was a dark olive-green, almost black, blending perfectly with the shadowed rock. The spores were produced in tiny, urn-shaped capsules that barely rose above the mat. It clung. It grew. It survived. The tiny mossy crevice was a pioneer of the vertical cliff, one of the first living things to colonise the bare rock in the deepest crevices. It captured moisture from the seeping water, trapped dust from the wind, and slowly, over decades, began the process of turning rock into soil. Mosses reproduce by spores, released from capsules on slender stalks. The tiny mossy crevice produced spores in tiny, dark capsules. The spores were carried by water trickling through the crevice, landing in other cracks, waiting for moisture to germinate. That strategy works when the cliff is stable and the crevices are undisturbed. It fails when the cliff crumbles and the rockslides fall. Cliff erosion and rockslides destroyed it. The cliffs where the tiny mossy crevice lived were soft, easily eroded by wind and rain. Over time, the rock crumbled, and the moss crumbled with it. At the same time, rockslides and cliff falls buried the crevices where the moss lived. A single rockslide could destroy decades of growth in a few seconds. The tiny mossy crevice, which grew only in the deepest, most stable crevices, could not survive. By the 1910s, it was gone. The last specimens were probably collected by a botanist who had no idea he was holding the final individual. He pressed them, dried them, put them in a drawer. And the cliffs fell silent. The larger mosses survived. They are tougher, more adaptable, able to grow on a wider range of surfaces. They are the survivors, the ones that kept their heads down. But the tiny mossy crevice is extinct. A few pressed specimens in a herbarium, a few fragments of its DNA, and the memory of a moss that used to grow in the deepest cracks of the cliffs, a hidden phantom in the stone. The hidden phantom has faded. The rocks are not as deep as they used to be.