The collection of the four fundamental mechanisms used in continuous wave (CW) DNP experiments are the Overhauser effect (OE), the solid effect (SE), the cross effect (CE) and thermal mixing (TM). The conventional wisdom states that the OE and the nuclear Overhauser effect (NOE) require rapid motion that governs the relaxation of the electron or nuclear spins and are typically observed in conducting solids (metals and low dimensional conductors) and liquids, respectively. In the case of OE DNP using electrons, near on resonance irradiation yields a symmetric absorptive DNP Zeeman field profile centered about the electron paramagnetic resonance (EPR) line. In contrast, the SE, CE and TM do not require dynamic spins and are observed in insulating solids and yield asymmetric Zeeman profiles. The SE dominates with narrow line polarizing agents (PA) and off-resonance irradiation excites the forbidden DNP transitions at ω ! ± ω " . The CE and TM rely on the three spin couplings and yield dispersive field profiles whose shape depends on the details of the EPR spectrum.