I?d like to show some examples from biology. Here is another favorite of mine.
This experiment shows the mapping from visual space to position on the visual cortex of a macaque monkey. The right image shows a section of the striate cortex of the left hemisphere stained with radioactive 2-deoxyglucose. When neurons are active, 2-deoxyglucose (a sugar) is transported across their membranes and trapped. When the brain is removed and an auto-radiograph created, the regions that were active appear as dark bands. (See p. 110 in Hubel for a nice explanation of the 2-deoxyglucose method.)
This self-illustrating phenomena shows the pattern in the brain when the monkey views a radial target with the only right eye open. This experiment showed that there is a direct mapping from visual field to the visual cortex, and that the transformation is logarithmic in r. That is, more space in the cortex is devoted to the foveal region of the retina than to the peripheral regions.
If you look closely, you can see that the dark bands are hatched. Is that real or an artifact?
Reference:
[1] Eye, Brain and Vision, D. Hubel ? This book is available online at http://neuro.med.harvard.edu/site/dh/index.html