A heat sink for cooling a heat generating device comprises a body part with a first surface for contacting the heat generating device, and a second surface contacting a cooling part, and the cooling part including a cooling structure. The structure density of the cooling structure decreases with increasing distance to body part. The cooling structure may be a three dimensional structure e.g. a grid or a lattice, but the cooling structure may also be fins projecting or extending from the second surface of the body part. The heat sink can be manufactured using additive manufacturing e.g. selective laser melting process (SLM). The heat sink can be made of metals e.g. aluminum, copper, ceramics e.g. aluminium nitride (AIN), silicon carbide or a composite containing graphite, graphene or carbon nanotubes.