Don't delay your care at Mayo Clinic
Brain tumor, breast cancer, colon cancer, congenital heart disease, heart arrhythmia. See more conditions.
Mayo Clinic offers appointments in Arizona, Florida and Minnesota and at Mayo Clinic Health System locations.
Subscribe to Housecall
Our general interest e-newsletter keeps you up to date on a wide variety of health topics.
Any guesses about this image? It's the lens of a baby's eye.
Twenty-three weeks into pregnancy, or 21 weeks after conception, a baby begins to have rapid eye movements. A baby's eyelids begin to open at 28 weeks into pregnancy, or 26 weeks after conception.
Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.
Check out these best-sellers and special offers on books and newsletters from Mayo Clinic.
A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.org," "Mayo Clinic Healthy Living," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.
This site complies with the HONcode standard for trustworthy health information: verify here.