Cross-section of <a href="https://en.wikipedia.org/wiki/en:3D_optical_data_storage" class="extiw" title="w:en:3D optical data storage">3D optical storage</a>
<a href="//commons.wikimedia.org/wiki/User:DnetSvg" title="User:DnetSvg">dnet</a>
self-made, based on <a class="external free" href="https://en.wikipedia.org/wiki/Image:WPgraphic1_J.jpg">http://en.wikipedia.org/wiki/Image:WPgraphic1_J.jpg</a> (PD)