Quantum Computers carry great promises for the future. By exploiting the power of quantum-mechanical principles like tunneling, superposition, entanglement and wave interference, computers can be built that have the (potential) power to solve mathematical problems that cannot be solved by any classical computing system available now or in the near future. Although quantum-mechanics sometimes appears elusive and counter-intuitive, the principles that underly quantum computers can be very well explained. In this talk, the fascinating principles behind quantum computers will be explained. Some common technologies will be shown, using these principles to build quantum computers and control them with high accuracy.