I'm a student in a field unrelated to biology or medicine, however I very much enjoy reading about it. I just read in Merck Manual that

Human cells vary in size, but all are quite small. Even the largest, a fertilized egg, is too small to be seen with the naked eye.

A very quick google search (caused by basic elementary school biology knowledge) results in Wikipedia article that says The egg cell is typically not capable of active movement, and it is much larger (visible to the naked eye)

Did I misinterpret something here, or I'm reading an unreliable source? Merck Manual was reccommended for learning about these things since it's maintained by MDs so I was just wondering. Thanks!

  • $\begingroup$ bird and reptiles ovum visible to naked eye; including the hen eggs that you eat on breakfast. So please edit the question title for human ovum or mammalian ovum that would help at a glance to figure out what you are trying to ask. $\endgroup$
    – user25568
    Commented Nov 4, 2016 at 2:55

1 Answer 1


The line that you quote from the Wikipedia page is talking about ova in general, whereas your question relates specifically to human ova. The "Human and mammal ova" section of the same article states that

The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a microscope or other magnification device.

With the stated average size of 0.12 mm in diameter (same Wikipedia article), an ovum is very, very small, but presumably a person can still see it unaided.


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