The columnar organization is currently the most widely held hypothesis to explain the cortical processing of information, making its study of potential interest to any researcher interested in the cerebral cortex, both in a healthy and pathological state. Enough data are now available so that the Blue Brain Project can realistically tackle a model of the sensory column in rat. Few will deny however, that a comprehensive framework of the function and structure of columns has remained elusive. One set of persistent problems, as frequently remarked, is nomenclature. "Column" is used freely and promiscuously to refer to multiple, distinguishable entities; for example, cellular or dendritic minicolumns (<50um), and afferent macrocolumns (200-500um). Another set of problems is the degree to which the classical criteria (shared response properties, shared input and common output) may need to be modified and, if so, how. A third, related set of problems is to define area-specific and species-specific variations. Finally, more of an ultimate goal than a problem, is to achieve fundamental understanding of what columns are and how they are used in cortical processes. Therefore, one of the major objectives is to translate recent technical advances and new findings in the neurosciences into practical applications for the neuroscientist, the clinician, and for those interested in comparative anatomy and brain evolution.