And we have 20 amino acids. And because this is less than 20, once again that means a pair of nucleotides cannot be used to basically build a single amino acid. So pairs of nucleotides cannot be used as well because that would only produce 16 unique possibilities. And it turns out that cells use triplet nucleotide sequences known as codons to encode for that amino acid. Because if we multiply four times four times four in our triplet, that would give us a value greater than 20. It would give us 64.