Genome sequencing has revealed that there is significant genetic diversity in the human population.Genome sequencing in the mouse population shows that the genetic diversity in the mouse is similar to the human.There are many experiments and observations that can be done only in mice and many others that can be done faster or better.We have set out to examine two classes of pheno-types, gene expression and brain morphology, using high and moderate throughput techniques in 99 different inbred strains of mice.For this first survey, we focused on the hippocampus due to its significant role in learning, memory, depression and other mood disorders, schizophrenia, Alzheimers disease, etc.The gene expression analysis shows that > 1% of the total genome has expression level controlled by a single locus.Allowing for the homozygous state and the sampling rate from the wild population we estimate that 4-8% of gene expression levels in wild-type mice (or humans) are controlled by single locus differences.Almost all of the 96 morphological traits assessed vary significantly; the bulk of this variation is NOT monngenic, i.e., it is controlled by two or more loci.The identification of the amount and extent of genetic diversity in a population is the first step toward a rational design of therapies and treatments targeted to specific genetically identifiable subpopulations.