The past few years have witnessed a revolution in the understanding of health and disease, brought on by the sequencing of the human genome and the creation of a map of human genetic variation. This revolution has been given a name: personalized medicine. The roots of personalized medicine are based in providing the right diagnosis and treatment to the right patient at the right time at the right cost.

People vary from one another in many ways - what they eat, the types and amount of stress they experience, exposure to environmental factors, and their DNA. Many of these variations play a role in health and disease. For example, the natural variations found in our genes could influence our risk of developing a certain disease, as well as how our bodies respond to that disease. The combination of these variations across several genes can affect each individual's risk of developing a disease or reacting to something in the environment, and can be one of the reasons why a drug works for one patient and not another.

Personalized medicine hopes to use these variations - both in the patient and in the molecular underpinnings of the disease itself - to develop new diagnostic tests and treatments and to identify the sub-groups of patients for whom they will work best. It can also help determine which groups of patients are more prone to developing some diseases and, ideally, help with the selection of lifestyle changes and/or treatments that can delay onset of a disease or reduce its impact.

Personalized medicine is poised to transform healthcare over the next several decades. New diagnostic and prognostic tools will increase our ability to predict the likely outcomes of drug therapy, while the expanded use of biomarkers - biological molecules that indicate a particular disease state - could result in more focused and targeted drug development. Personalized medicine also offers the possibility of improved health outcomes and has the potential to make healthcare more cost-effective.