CRISPR contributed to Science’s Breakthrough of the Year and was also nominated for the Breakdown category by the same journal. The second nomination was an easy guess: He Jiankui and its baby-editing claim were also mentioned in Nature’s 10 for 2018. Much more interesting is the decision to celebrate cell-barcoding, the CRISPR-based technique used to track embryo development in stunning detail and over time.

Visitors to Science’s website were in agreement with reporters and editors: exploring organisms cell by cell is the accomplishment of the year. Editor-in-chief Jeremy Berg explains why it deserves the accolade: the application of this tag-analyze-assemble approach to one of the most fundamental and fascinating processes in biology—the seemingly miraculous transformation of single cells into complex organisms—is providing rich information about cell-type inventories and lays the foundation for many future studies.