Quantum secure direct communication transmits secret information directly without encryption. Recently, a research team led by Prof. Gui-Lu Long from Tsinghua University proposed a measurement-and-device-independent quantum secure direct communication protocol using Einstein-Podolsky-Rosen pairs. This protocol eliminates all loopholes related to measurement devices, which solves a key obstacle in practical quantum secure direct communication. The protocol has also an extended communication distance, and a high communication capacity.