Atomic coherence originates from the superposition of quantum states of the atom and can enhance measurement sensitivity and enable low-light level quantum and nonlinear optics, thus has become a key resource in fields of precision measurements and quantum information science. In this talk, I will give several examples from our experiments using anti-relaxation coated atomic vapor cells with long coherence lifetime. For the precision measurement part, I will describe a sub-coherence-lifetime spectroscopy technique giving resonance linewidth of 0.1 Hz, and how we use it to achieve photon-shot-noise limited magnetometry. Ongoing experiments of breaking this limit using squeezed-light will be presented, as well as progress in preparing a large spin squeezed state. For the quantum optics part, I will show how atomic coherence transport can be employed to make a beam splitter for squeezed light, and how it mediates linear or nonlinear coupling of spatially separated light modes, giving rise to an anti-parity-symmetric optical Hamiltonian. In the end, I discuss future prospects in this unique system.