This image shows the cobalt defect fabricated by the study team. The green and yellow circles are tungsten and sulfur atoms that make up a 2D tungsten disulfide sample. The dark blue circles on the surface are cobalt atoms. The lower-right area highlighted in blue-green is a hole previously occupied by a sulfur atom. The area highlighted in reddish-purple is a defect – a sulfur vacancy filled with a cobalt atom. The scanning tunneling microscope (gray) is using electric current (light blue) to measure the defect’s atomic-scale properties.