This is the fourth year since the Hong Kong Science Museum has started hosting the HK SciFest in 2014. Through this fabulous large-scale event, we aimed to collaborate with scientific institutes and organisations to provide interesting scientific activities to elevate the public awareness and interest in science and technology. We organised a series of "Medicine and Health" thematic programmes this year which helped the public to understand the scientific concepts behind western and Chinese medicines, and recognise the contribution of medical research and disease treatments to our health. HK SciFest 2017 offered 172 scientific activities, including exhibitions, visits and guided tours, science workshops, family days, science drama shows, fun experiment classes, science lectures and science competitions. Special programmes included the Fun Science Carnival and the Science Communication Week that marked the beginning of the SciFest, and the Science Alive series of education activities. Experts on science communication from the UK and USA were invited to conduct science performances for the public and share their experience with local science educators in workshops. Please run back over the festival through this video!