Prior to discussing individual visualization techniques and tools available, we would like to note two overarching characteristics of genomic data that are highly relevant to their visualization. First, huge quantities of data need to be dealt with, as visualization tools are o©en deployed in largescale genomic analysis. For example, high-throughput DNA sequencing produces large amounts of sequence data in a relatively short time. We also
need to access and utilize ever-increasing quantities of existing public data accessible from online data repositories, ranging from the DNA sequence ¥les themselves to genome annotations, including taxonomic classi¥cations. As a rule, some sort of semantic zooming mechanism (Loraine and Helt, 2002) is required to enable the user to explore the genomic data set in its entirety, as well as in speci¥c detail. ™is in turn requires an underlying multiscale, or scalable representation of a complex data set, to accommodate the appropriate display at several di¤erent levels of detail.