The Allen Institute for Brain Science has released a comprehensive 'atlas' map of the mouse brain that was taken with a resolution of 100 um^3. The map shows comprehensive gene expression data in every part of the brain and was taken by collecting thin slices of brain tissue, then using labeled RNA probes to detect mRNA concentrations one gene at a time. More than one mouse brain was needed for this procedure, so a group of inbred male mice were all sacrificed at the same age, on the same day, at the same time to insure that the expression patterns would be nearly identical.
With this map, researchers can look not only at accurate anatomical layouts, but actual functional groupings of brain tissue according to gene expression. This should allow for much enhanced experiments asking more indepth questions as to what specific parts of the brain interact with one another.
The software is free to download and you can search by gene, or brain area. It is really quite amazing and should lead to many discoveries in the future.