Twenty years ago, results from the Human Genome Project revealed that the human genome contains 20,000 protein-coding genes.
At the time, it was thought that the vast majority of the human genome would consist of instructions for making proteins. However, Instead, it transpired that less than two percent of the three billion letters of the human genome are dedicated to proteins.
The remaining 98 percent has been described as 'dark matter' or 'junk DNA'. This BBC Future article investigates how the human genome's noncoding regions may be crucial to our understanding of humanity.