Hybrid fuzzing has been extremely successful in bug vulnerabilities. This lecture will briefly 1) overview the concept of hybrid fuzzing, 2) showcase how it addresses the limitations of fuzzing and concolic execution by combining both approaches, 3) highlight both its strengths and weaknesses, and 4) present how QSYM, a fast concolic execution engine, addresses some of the limitations, especially on integrating the symbolic emulation with the native execution using dynamic binary translation. We will also cover some of the follow-up works of QSYM and in the area of hybrid fuzzing in general.