An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.
The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.
Get the latest public health information from CDC
Get the latest research information from NIH | Español
Which of the figures in the picture do you think would measure the tallest with a ruler?
Don't measure -- just guess!
They are all exactly the same.