Below left: Refinement of the cover so that no point in the shape is contained in more than 3 sets.
Below right: An attempt to refine the cover so that no point in the shape would be contained in more than 2 sets. Notice how some set border intersection points cannot be covered.
Purpose: To illustrate the role of covers in the definition of topological dimension, figure 2 of 2.
(Above: Cover (four colourful sets) of a planar shape (dark).
Below left: Refinement of the cover so that no point in the shape is contained in more than 3 sets.
Below right: An attempt to refine the cover so that no point in the shape would be contained)