Researchers created embryos from stem cells that form a brain, a beating heart, and the foundations of all the other organs of the body.

The human genome is littered with “selfish genetic elements,” which do not seem to benefit their hosts, but instead seek only to propagate.

In a pair of world firsts, scientists have 3D printed human testicular cells and identified promising signs of sperm-producing capabilities.

These sperm were successfully used to produce healthy, fertile offspring.

For species that rely on sexual reproduction, offspring can only happen if sperm from the male fertilize eggs from the female.