With the development of technologies coupled with fundamental scientific inquiry, the quantum control gradually enters into people's horizons. More and more theoretical and experimental researches in this area have been driven. A lot of sophisticated control methods, such as dynamical decoupling and coherent-feedback control, have been proposed. The experience has shown that systematic use of quantum control theory can lead to significant improvements in technologies ranging from magnetic resonance to prototype quantum computers. In this work, we mainly briefly introduce two widely-used quantum control protocols, namely open-loop control and closed-loop control, and illustrate the significant role played by the quantum control using two explicit examples. Obviously, this is only a tip of the iceberg.