How can an X chromosome be nearly as big as the head of the sperm cell?

No, this isn't a mistake. First, there's less DNA in a sperm cell than there is in a non-reproductive cell such as a skin cell. Second, the DNA in a sperm cell is super-condensed and compacted into a highly dense form. Third, the head of a sperm cell is almost all nucleus. Most of the cytoplasm has been squeezed out in order to make the sperm an efficient torpedo-like swimming machine.

From the archive:

All movement in Celestia is seamless; the exponential zoom feature lets you explore space across a huge range of scales, from galaxy clusters down to spacecraft only a few meters across.

See also, The Zoom Quilt (now here):

What M.C. Escher would do with Flash.

Barrett Sheridan:

Zooming represents an upgrade from the second- and third-best methods for accessing information (scrolling and linking) to the best option: displaying information like a landscape, and giving people the chance to zoom down to the details.

Charles C. Mann:

I felt alone and small, but in a way that was curiously like feeling exalted.

Cell Size and Scale