This chapter focuses on a gas-aggregation technique to prepare magnetic nanoclusters with controllable cluster sizes and size distributions. The review includes current research on nanoclusters, such as uncoated and oxide-coated Fe, Co and Fe clusters and clusters made from alloys, but special emphasis is on highly anisotropic L10-ordered FePt clusters, which are of potential interest for magnetic recording with ultrahigh areal densities of more than 1 Tera bit/in2. In particular, we discuss magnetic and structural properties of FePt nanoclusters and thin films. Another approach discussed in the chapter is to create cluster nanocomposites by multilayering with post-deposition annealing. The advantage of this method is that the clusters can be oriented along a desired easy axis. One example is L10-(001) oriented FePt nanocomposite films with a FePt cluster size of about 5 nm
