Nanosized Co pillars were grown in Au(111) using a novel deposition process. Starting from a self-organized array of Co dots on the Au(111) surface, we alternatively deposit Au (0.9 ML) and Co (0.1 ML). Under appropriate conditions, the newly deposited Co atoms assemble into dots, vertically self-aligned and in direct contact with the Co dots from the previous layers. This way, pillars 8 nm high and with a 2:1 vertical aspect ratio were fabricated. It is argued that the growth process is driven by parameter misfit and surface energy effects, and should thus occur for other pairs of elements than (Co,Au). From the superparamagnetic regime, we deduce that each pillar behaves like a single magnetic entity. The onset of perpendicular remanence occurs around room temperature, instead of 20 K for the initial flat dots. In terms of applications, the main drawbacks of self-assembled and organized nanosized magnetic systems are the small amounts of material contributing to magnetic effects, and the superparamagnetism blocking temperature, generally well below RT. The pillar growth process is a good candidate to solve them simultaneously.