Small pebbles in the Lake Tagish meteorite seen through a Scanning Electronic Microscope (SEM). The Tagish Chondrule is a solidified droplet of molten rock that crystallized (mostly) into the mineral Olivine early in the solar system. The color is due to optical luminescence under electron bombardment. The incident electrons excite electrons in the material, but the de-excitation takes place in a process that involves the release of visible light photons - this is called 'cathodoluminescence' and is used to reveal fine textural details that are commonly invisible to other imaging methods, such as crystallographic defects and trace level 'contaminant' elements.