Plasmids are the key to genetic engineering. You can't just take a string of genetic code, throw it into a pot of DNA, give it a shake and expect a cure for cancer to fall out. Plasmids are tiny loops of genetic material that scientists use to courier desired genes into the heart of a cell, its DNA. Pretty much all genetic engineering depends on plasmids, and keeping track of them can be a hassle. In the past, scientists who wanted to use plasmids had to more or less build them from scratch, which can be a slow and time-consuming process.