Quantum effects can enhance the precision and sensitivity in detecting weak fields (originating either from neurons in brain, or from cosmos). The diamond spin defect turns out to be a surprisingly versatile and well controllable solid state quantum system, with long relaxation and coherence time of their quantum state with guaranteed high fidelity single spin control even at room temperatures. Precision sensing using quantum states of such defects usually relies on accurate measurements of their quantum phase, and is called quantum sensing, and the defects quantum sensors. At PI3, we explore how quantum sensors powered by defects in solids could be used to achieve high sensitivities in detecting extremely weak fields, either it be a pico-Tesla magnetic field1 or a μV/m electric field2, arising from spins and molecules, with a large bandwidth (15 orders) in resolution ranging from giga- to micro-Hertz fields. We also study their role in assisting dark matter studies through detecting axion-like particles and WIMPS.