The creation of embryos specifically for research purposes.
Sperm Count
A count of SPERM in the ejaculum, expressed as number per milliliter.
Embryo, Mammalian
The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.
Sperm Head
The anterior portion of the spermatozoon (SPERMATOZOA) that contains mainly the nucleus with highly compact CHROMATIN material.