<a href="https://en.wikipedia.org/wiki/Scanning_electron_microscope" class="extiw" title="en:Scanning electron microscope">SEM</a> micrograph of a sectioned tennis string. Courtesy of Prof Claire Davis and Elizabeth Chandler, School of Metallurgy and Materials, University of Birmingham.
<a href="//www.flickr.com/people/41639353@N08" class="extiw" title="flickruser:41639353@N08">CORE-Materials</a>
CC BY 2.0
<a href="//commons.wikimedia.org/wiki/Flickr" class="mw-redirect" title="Flickr">Flickr</a>: <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/41639353@N08/4398469894">Structure of a tennis string</a>