The skull of a chicken embryo (left) has a recognizable beak. But when scientists block the expression of two particular genes, the embryo develops a rounded "snout" (center) that looks something like an alligator's skull (right). Bhart-Anjan S. Bhullar hide caption

itoggle caption Bhart-Anjan S. Bhullar

The CRISPR enzyme (green and red) binds to a stretch of double-stranded DNA (purple and red), preparing to snip out the faulty part. Illustration courtesy of Jennifer Doudna/UC Berkeley hide caption

itoggle caption Illustration courtesy of Jennifer Doudna/UC Berkeley

This micrograph shows a single mitochondrion (yellow), one of many little energy factories inside a cell. Keith R. Porter/Science Source hide caption

itoggle caption Keith R. Porter/Science Source

Genetically modified wheat has been discovered growing in a field in Oregon. GMO wheat is not approved for sale in the U.S. Above, a wheat field in Arkansas. Danny Johnston/AP hide caption

itoggle caption Danny Johnston/AP

"Child-robot with Biomimetic Body" (or CB2) at Osaka University in Japan in 2009, where the android was slowly developing social skills by interacting with humans and watching their facial expressions, mimicking a mother-baby relationship. Yoshikazu Tsuno/AFP/Getty Images hide caption

itoggle caption Yoshikazu Tsuno/AFP/Getty Images

An image of researchers at Oregon Health & Science University removing the nucleus from the mother's cell before it's inserted into the donor's egg cell. Courtesty of Oregon Health & Science University hide caption

itoggle caption Courtesty of Oregon Health & Science University