The invention pertains to a device and a process for the production of nanofibers, in particular, nanocellulose from a fiber-containing mixture of substances, whereby the device is formed including at least one discharge element with a discharge opening for the passage of a fiber-containing mixture of substances, at least one feeding device for the supply of the fiber-containing mixture of substances to the discharge element with a predeterminable process pressure, at least one positioning device for the positioning of the discharge element and whereby, for the disintegrating of the fiber-containing mixture of substances, a moveable processing body is arranged opposite relative to at least one discharge element whereby on the passage of the fiber-containing mixture of substances through the discharge element a slit-like processing area is formed between the discharge element and the substance mixture-affected partial surface of the moveable processing body.