Sildenafil citrate crystals extracted from a liquid sildenafil (generic Viagra) product, examined under polarised light. This image was generated with the use of a Leica DM2000 microscope at <a href="https://en.wikipedia.org/wiki/Robert_Gordon_University" class="extiw" title="w:Robert Gordon University">Robert Gordon University</a>, Aberdeen
<a href="//commons.wikimedia.org/wiki/User:Nick" title="User:Nick">Nick</a>
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<span class="int-own-work" lang="en">Own work</span>