Michigan State University researchers have solved the mystery of a poorly understood sperm structure called the cytoplasmic droplet, or CD. The CD is an expanded cytoplasm — watery, gel-like cell contents enclosed by cell membrane — found close to the head, at the neck of the sperm, in all mammals, including humans. This new genetic model is the first of its kind.

Despite being first discovered more than 100 years ago, it’s been unclear how the CD forms and what its function is due to the lack of molecular and genetic tools to study it.

Scientists have often disregarded it, but it can’t be ignored anymore said Chen Chen, an associate professor in the Department of Animal Science and the Reproductive and Developmental Sciences Program in MSU’s College of Agriculture and Natural Resources.