For billions of years, life on Earth has relied on a genetic code built from only four chemical letters.
These four letters, A, T, C, and G, spell out the instructions for every plant, animal, and microbe.
Researchers at the University of California, San Diego have now shown that this code can be expanded.
They created four additional synthetic letters, effectively doubling the alphabet to eight.
Crucially, a key cellular enzyme, the machine that reads and copies genetic material, handled the expanded code accurately.
Being able to read these extra letters is an essential step toward using them reliably.
Scientists say the breakthrough could dramatically increase how much information DNA can store.
It may also give researchers new tools to design medicines that natural DNA cannot easily produce.
Even so, the technology is still experimental and far from everyday use.