Imaging molecules with atomic force microscopy. These molecules are involved in charge transfers such as energy transport in living systems. The molecules are being imaged as part of research into molecules in different charge states. From top to bottom, the molecules are: azobenzene, pentacene, TCNQ (tetracyanoquinodimethane) and porphine. The charge states are by column, from left to right: 1st column (blue) for positive charge; 2nd column (green) for neutral state; 3rd column (orange) for negative charge; 4th column (red) for doubly negative charge. Image published in July 2019.