A new kind of cross-effect (CE) dynamic nuclear polarization (DNP) using biradicals with exchange couplings larger than the g-anisotropy or g-difference is proposed. The strongly coupled biradicals can be described with a combination of singlet ๐0 and triplet ๐0,ยฑ1 states. Despite being invisible to ยตw irradiation and spectral detection for the singlet state, ๐! โ ๐! singlet-triplet transition by hyperfine couplings can occur driving nuclear spin flip for cross-effect DNP process. The ๐0 state population and spin alignment order can be generated by selectively saturating one of the ๐0 โ ๐ยฑ1 transitions. Introducing dipolar couplings and frequency differences between the two electrons can remove the degeneracy between the two triplet transitions enabling selective saturation to obtain singlet-to-triplet cross-effect (ST-CE) DNP.