With great power comes great color SnO
2 nanocrystals coated with protective polydopamine appear red when fully charged and green in a discharged state. In their Communication on
page 1869 ff., Z. Lin et al. describe polymer-template-guided formation of SnO
2 nanocrystals. The material was applied as an anode in lithium-ion batteries––achieving excellent rate capability, long-term stability, and operability over a range of current densities.