The first steps of human development—those that occur within the first few weeks of pregnancy—remain mysterious in many ways. Within a week of fertilization, human embryos form a blastocyst, which ...

Many state legislatures are seriously considering human embryos at the earliest stages of development for legal personhood. Total abortion bans that consider humans to have full rights from the moment ...

A gene that turns on very early in embryonic development could be key to the formation of the placenta, which provides the developing fetus with what it needs to thrive during gestation. The placenta ...

Using human stem cells, scientists have created human embryo-like structures inside petri dishes. These lab-grown blobs develop multiple structures that mimic a human embryo after implantation into ...

The majority of fertilized eggs die and are resorbed into the body. ZEISS Microscopy/Flickr, CC BY-SA As an evolutionary biologist whose career has focused on how embryos develop in a wide variety of ...