The diffraction limit in direct-laser-writing (DLW) lithography can be circumvented by selective inhibition of the polymerization. By combining nanosecond transient absorption spectroscopy and density functional theory it is demonstrated that polymerization inhibition is possible by a direct absorption of the lowest triplet state. Polymerization inhibition by triplet state absorption (TSA) has the potential to bring DLW lithography into the nanometer scale.