The immune system is constantly on the lookout for threats, but cancer isn’t always easy to spot. Some cancer cells can fly under the radar. Now, advanced sequencing technologies are enabling scientists to investigate the unique genetics of both cancers and immune responses in individual patients. This means researchers can develop treatments that boost the immune system and help the body win its battle against cancer. This video from Nature Reviews Genetics and Nature Reviews Cancer is freely available online thanks to support from Illumina, Inc. This video is editorially independent and the sole responsibility of Springer Nature Limited.