The human imagination is limitless. Internet of Things (IoT), driverless cars, drones, virtual reality (VR) and long-sustaining batteries are hot topics in the tech sphere, and though some parts of those visions have indeed manifested themselves to the real world, mostly in the form of compact devices and viable prototypes in the lab, the reality is that many of them remain only as concepts.
Limitations in software and hardware, and the time it takes for the public to absorb those concepts or ideas are some of the obvious hurdles. Then there is the most fundamental limitation of all: Materials. 
[1} By Cho Mu-Hyun for ZDNet