Abstract: Micrometric separator (1) for biomasses (100) in particles, of the type comprising at least one first crushing stage (2) wherein said particles are introduced dispersed in a conveying fluid bed, and first means (110) for conveying said particles in said fluid bed. The afore said first crushing stage (2) comprises a first crushing chamber (5) for reciprocal collisions of particles, that has at least one first revolving disc (7) provided with first members (9) for generating at least one turbulent flow in the fluid bed, and at least one first contrast body (8), in front of the first revolving disc (7), as well as one or more outlets (22) of the fluid bed, the first contrast body (8) being provided with at least one inlet (6) having an inflow section with the axis substantially incident to the first revolving disc (7).