Abstract: Human System Integration (HSI) is about orchestrating technology, organization and people in a flexible way. Flexible sociotechnical systems, called “FlexTech,” are based on anticipation, preparation, creativity and experience. These systems contrast with those stemming from technology-centered engineering that produces objects and machines with the immensely codified and rigid practices we know today. Most of the time, technologies are designed and developed for normal situations, leaving users to manage abnormal and emergency situations themselves, sometimes under unforeseen, extreme and/or dangerous conditions. Putting humans at the center of the design of flexible sociotechnical systems means imagining possible futures, modeling them, simulating them and leading them down the right paths. This keynote is for the designers, who seek to better understand the roles of humans and organizations developing complex life-critical systems. It is also for those who train future human-centered designers who will have to take into account the well-being, safety, sustainability and efficiency of the actors of future sociotechnical systems. The aim of the flexibility challenge is to put the artificial at the service of the natural, and not the other way around.