Structure inside autoclaved aerated concrete (AAC) with various crystals (tobermorite, CaSO<sub>4</sub>, Jennite etc). Sometimes we search for one thing but discover another. This CaSO<sub>4</sub> crystals looks like space station.
<a href="//commons.wikimedia.org/w/index.php?title=User:FUM_2017&amp;action=edit&amp;redlink=1" class="new" title="User:FUM 2017 (page does not exist)"> Tarmo Tamm (<i>project manager</i>), Markus Otsus, Artur Kaljo</a>
CC BY 4.0
This scanning microscopy image was taken at the <i>Institute of Technology University of Tartu</i>   during the research work of lightweight concretes