ArrayExpress can be used to retrieve data and then re-analyse it, using the appropriate data analysis software. Often, data deposited in public repositories can be used to answer different biological questions from the one asked in the original experiments.
The example provided here refers to a large meta-analysis project carried out on all publicly available data sets, generated on the Affymetrix GeneChip Human Genome U133A. This analysis resulted in a global map of human gene expression (10) and the data associated with such analysis was resubmitted as a new experiment (E-MTAB-62). It is also available through the Gene Expression Atlas.