Source: dist/css/acc_boot.css, line 8835
5.9.5.4 Image Thumbnails
images thumbnails are used to display the images associated with the content. the aspect of the images are 1:1.
Example
<div class="aspect_1x1 flex_none" style="width: clamp(75px, 10vw, 125px);">
<img src="https://picsum.photos/110/110" alt="" class="w_100">
</div>