This modified wide-field microscope was used to perform spatially-resolved Continuous Wave ODMR (CW-ODMR), a technique to determine the sublevel structure of the ground state. The ground state of the NV center is a spin triplet, with the |𝑔, 𝑚 𝑠 = ±1⟩ state levels upshifted by 2.87 GHz with respect to the |𝑔, 𝑚 𝑠 = 0⟩ state. Continuous irradiation with a 532 nm laser polarizes the |𝑔, 𝑚 𝑠 = 0⟩ ground state level through spin dependent transitions from the excited state through the metastable singlet states. Different laser power levels in the range 1-30 mW are used for this experiment. MW frequency is swept in the 2.75-3.00 GHz region at a fixed power output of 15 dBm to detect 13 C sidebands and NV -central resonances. In fact, when the MWs are resonant with the |𝑔, 𝑚 𝑠 = 0⟩ ↔ |𝑔, 𝑚 𝑠 = ±1⟩ ground state transition, the darker states |𝑔, 𝑚 𝑠 = ±1⟩ become populated, and a drop in the fluorescence (a "dip" in the ODMR spectra) is recorded. The ODMR contrast provides a measure of spin polarization of the |𝑔, 𝑚 𝑠 = 0⟩. However, the ODMR spectrum is also affected by the relative contribution from NV 0 fluorescence, which is not modulated by MW and offsets background fluorescence. An increase in ODMR contrast may thus indicate increased polarization of NV -, or decreased concentration of NV 0 s. The sequence of laser and MW irradiation to perform the ODMR experiments is described in the box of Fig. .