Sleep is essential for brain functionality and overall health but understanding how sleep delivers its beneficial effects remains largely unknown. Sleep researchers are exploring new and unbiased approaches that can take sleep to a systems level. In one such approach, referred to as 'systems genetics', inferences about biological phenomena can be made by linking together several levels of information from DNA to phenotype via gene expression, proteins and metabolism at the level of a population. Systems genetics offers a global and interconnected view of biological phenomena and is therefore considered critical towards predicting disease susceptibility.