Nendo is made of finer grains than grains of sand, which are originally lava and volcanic ash from volcanic explosions. Over a long period of time, a portion of this lava was blown by the wind, becoming finer and finer, and then being carried away by rain, rivers, and the sea, it was collected in one place and gradually accumulated.
As they are piled up, the force and weight of the ground presses them down harder and harder. There are large rocks here, of course, but it also contains stones, sand, and the finest of clay.
After a long time, smaller grains of sand, animal bones, and plant matter accumulate to form a very fine-grained clay.
This is how we use the clay created by nature.

Paper clay is made by cutting newspaper into small pieces, soaking them in water, and adding an adhesive to make a sludgy pulp-like substance. Recently, there is also clay made from plants.