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There are more nerve cells in one human brain than there are stars in the Milky Way.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
HIV testing reach is still limited. An estimated 40% of people with HIV (more than 14 million) remain undiagnosed and do not know their infection status.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Many supplement containers do not even contain what their labels say. There are many documented reports of products containing much less, or more, that what is listed on their labels. They may also contain undisclosed prescription drugs and even contaminants.