It’s a scientist’s nightmare: Spending time and resources to investigate a biological phenomenon only to learn later that your cells are not what you think they are—their true identities hidden. As a result, all of the data that you’ve generated with those cells, published and unpublished, are cast into doubt. You thought that you knew your cells, that you could trust them, but your trust was misplaced. At some point, perhaps even before the traitorous cell line entered your laboratory, the cells were mislabeled, misidentified or contaminated with another cell line. It didn’t have to be this way. There are easy steps you can take to prevent the headache and heartache of cell line misidentification and contamination.