Quantum spin systems are insulating crystals containing regular array of atoms carrying spin S = 1/2 or 1, described by simple spin Hamiltonians. In low-dimensional model compounds, we study by Nuclear Magnetic Resonance (NMR), which is a microscopic probe to magnetism, the magnetic-field-induced "exotic" phases, such as the Bose-Einstein condensate, magnetization plateaus or spin-nematic phase.