These are the fibers located in the upper shoes that constrict the movement of the legs. This provides maximum support, stability, and is also to reduce the weight of shoes.
It is a completely new foam, which is composed of a single piece of material. Thanks to the modern processing method, the design of the midsole is designed so that at specific places, which are most loaded during running, the shoe can be more attenuated. Conversely, in other places where much damping is not needed, the shoe is lightweight. You may notice the deeper parts that show more cushioned surfaces, even the shallower ones that create more strength.