English: A caddisfly larva (Trichoptera) photographed under a microscope using a 4x objective and dark-field microscopy. The specimen was collected from a pond in Rakvere, Estonia, in May 2021. Caddisfly larvae are true underwater architects - they build protective cases using special waterproof 'glue' or silk to bind together various particles found in water. The image clearly shows the larva's self-built protective case made of silk-cemented particles, creating a beautifully shimmering mosaic-like structure. The image was captured using dark-field microscopy, where light hits the specimen from the sides, particularly emphasizing the texture and fine details of the protective case. The image was created using focus stacking technique, which ensures great depth of field throughout the subject.