5G is envisioned to support unprecedented diverse applications and services with extremely heterogeneous performance requirements, i.e., mission critical IoT communication, massive machine-type communication and Gigabit mobile connectivity. This imposes enormous challenges to fulfil the key performance requirements, in particular, mission critical IoT communication, which calls for a dramatic paradigm change in 5G. This paper presents vision and challenges of mission critical IoT scenarios and the enabling technologies in 5G. Several research opportunities are given as example for inspiration purpose.