The crystals might be 3-hydroxy-bio-phenol, but they are nicknamed by Masha Aleksich as the "marshmallow samples" because they resemble tiny marshmallows in the images. It’s moments like this ...

This reaction can be used as a test for phenol groups. Mix several drops or a few crystals of compound to be tested in a beaker or in a 200mm test tube. Add a few drops of 1% FeCl3. As a control, add ...