sperm

Researchers are inching closer to creating human eggs and sperm in the lab that carry a full complement of anyone's DNA. It could revolutionize fertility treatment and raises huge ethical questions.

For decades researchers have struggled to find a contraceptive methods for males. A new fast-acting compound shows promise — assuming it turns out to work as well in men as in mice.

Data from nearly 43,000 men around the world found that sperm counts dropped by more than half in Western countries. It could reflect a decline in health overall, scientists say.

It's not unusual for males to try to impress females with big body parts. Consider antlers on deer, or elaborate tails on peacocks. Some male fruit flies take a different approach: giant sperm.