Both somatic and germline mutations are important when we consider a patient’s care. We sequence the DNA from a patient’s tumour and healthy cells. We compare the two sequences. This gives insight into the exact nature and genomic changes that are causing an individual’s cancer. This information can improve diagnosis. It can also help clinicians to select the treatments most likely to be effective in each individual case. Genomic tests can also show which patients are not likely to benefit from a specific treatment. This can save unnecessary treatments and toxic side effects. Genomics makes personalized medicine possible – with a real impact on patients and their health outcomes.