Technological breakthroughs often lead to both wonderful opportunities for advancement and potential for abuse. Nuclear physics and the internet are two undeniable examples. A third example was prominent in the news recently when a scientist in China, Dr. He, reported that he had genetically modified the DNA of twin girls using a very powerful new genetic tool known as CRISPR. The modification he claimed to have made (a claim that is unverified at present) is that he removed, or “knocked out” a molecule known as CCR5 that is known to be the entry point of the HIV virus into cells. His stated goal was to increase the ability of these girls to resist HIV, the virus that causes AIDS.