This paper discusses the cluster analysis and visualisation tool, the self-organizing map (SOM). The pros and cons of different network sizes are discussed, in particular how they are suited to the purposes of direct data browsing and also the cluster analysis with U-matrices. The tree-structured SOM (TS-SOM) [4, 5] is proposed as a method of acquiring multi-resolution/multi-purpose mappings of a given input space. The TS-SOM is discussed in detail and a novel modification to the algorithm that improves its reliability as a multi-resolution visualization method is presented.