One of the most pressing issues in lung cancer research is in identifying patients who could benefit from a particular drug, both to increase their chances of having a good outcome and to spare everyone else from an ineffective drug with unnecessary toxicity. There have been some exciting advances in this field, but before I elaborate I want to give some (simplified) background on how drugs are traditionally developed. Classically, potential cancer drugs are tested on cancer cell lines in a Petri dish, and if the drug appears to kill the cells, it is then tested in animals.