[Pt(L3)Cl]+ can also produce two‐photon‐induced luminescence at room temperature upon excitation at 700 nm from a mode‐locked Ti:sapphire laser. Its two‐photon absorption cross‐section in DMF at room temperature was measured to be 28.0×10−50 cm4 s photon−1. [Pt(L3)Cl]+ is able to selectively stain the cell nucleolus. This has been demonstrated by two‐photon confocal imaging of live and methanol‐fixed