Basic scale concepts illustrated with a spatial scenario. “Extent” and “grain” are illustrated for a simple case of contiguous coverage. Scale as “level” is illustrated here with an example of three discrete, spatially-nested units at which some inferences might be made (e.g. for mean vegetation height). A non-spatial example could be for three levels of organisation: suppose that biomass densities were averaged over a single grass species, over all grass species and over all herbaceous vegetation within the circular quadrats.