The present invention relates to a classifying fluid bed granulator, comprising a granulation chamber with a fluidizing air chamber (7) with a bed floor (10), a ceiling (3c), an end wall (3d), a feed inlet (5), a seed inlet (6), an outlet (4) defined by walls (3a, 3b) for air, and an outlet (9) for produced granules. The granulation chamber is divided into an agglomeration and seed control section (1) and a granulation and classification section (2) where said section (2) is divided into two or more consecutive compartments having an asymmetric design. Section (2) may contain tilted baffle plates (12). Furthermore, the present invention relates to a method for fluid bed granulation of a feed being a solution, slurry, melt, emulsion, suspension or solids into granules of a desired classified size. Inlet seed particles are given a controlled size in an agglomeration and seed section ahead of being granulated with the feed in a granulation and classification section. The classification of the granules is performed in asymmetric compartments in the granulation and classification section.