Internet users have a variety of format options in which to store their movies, and biologists have now joined the party. Researchers have used the microbial immune system CRISPR–Cas to encode a movie into the genome of the bacterium Escherichia coli.The technical achievement, reported on 12 July in Nature, is a step towards creating cellular recording systems that are capable of encoding a series of events, says Seth Shipman, a synthetic biologist at Harvard Medical School in Boston, Massachusetts. While studying brain development, Shipman became frustrated by the lack of a technique to capture how cells in the brain take on distinct identities. This inspired him to explore the possibility of making cellular recorders.