Copyright 2020 Exstrom Laboratories LLC Longmont, Colorado
Authors: Stefan and Richard Hollos
All images in the Macro and Micro Picture of the Day are licensed under the Creative Commons Attribution 4.0 International License.
Here is an infrared detector (LTR-301). In particular, it's an NPN phototransistor. It is 4.4 mm wide.
Equipment used: Canon EOS Rebel T5i with a standard zoom lens (EF-S 18-55 mm) on a 49 mm long extension tube.