Nova ScienceNow | RNA, the close chemical cousin of DNA, was once thought to be a bit player in the life of a cell, but not anymore. RNA is now at the heart of a scientific and medical revolution. It’s a revolution that started with the cultivation of a purple petunia, and it has led scientists to what may be the most important advance in biology in decades.

Through a process known as RNAi (the “i” is for interference), researchers have a new way to shut off specific genes, yielding insights into the human genome as well as providing potential treatments for a wide range of diseases.