Experimental cell biology is limited by the requirement for direct observation or destructive analysis of the cells being studied. This is particularly problematic when studying a complex, developing system such as the brain. To circumvent this limitation, I have pursued a new approach: the logging of biological events as coded nucleotides, written into the genome of a living cell. These organized changes to genomic DNA can store data during an event of interest, to be collected later by sequencing. I will display a functional version of this approach in prokaryotes that uses the CRISPR-Cas adaptive immune system, and discuss opportunities to use this molecular recording system to understand neurodevelopment.