DNA can be chemically synthesized in the lab — one letter at a time. Scientists build custom sequences by adding A, T, C, and G bases in a precise order, using chemical reactions on a tiny solid surface. Once complete, the strands are removed, purified, and sometimes stitched together to make longer chains.

This technique is behind everything from DNA data storage to genetic testing and cutting-edge therapies. DNA doesn’t just carry genetic instructions — it can store digital files too. Scientists have figured out how to translate binary code (0s and 1s) into the four DNA bases: A, T, C, and G. Using this method, they’ve encoded everything from books and images to a short film into synthetic DNA strands.

In one breakthrough, a Harvard team stored an entire book — including illustrations — in DNA. Another group encoded a GIF of a galloping horse, making it the first movie ever stored in biological form.

Why bother? DNA can store over 200 petabytes in just one gram and lasts thousands of years. It may be the future of archival storage — hiding tomorrow’s files in biology’s oldest code.