What makes smart cities smart Evolving technologies are reshaping our lifestyles much faster than we even realize. Once the storylines of science fiction also gradually appeared in front of our eyes, smart city came into being. But, what makes smart cities smart? First of all, smart city is the inevitable outcome of the development of human technology. A large number of population relocate to cities, beyond the load of the city To meet the challenge, cities need to digitize and modify infrastructures so that we can ensure the proper water supply and cater other resources demands. The more radical approach to deal with the resource problem is to build entirely new smart cities ,like Masdar city. Then, the government support is essential . Government has provided institutional and financial guarantees for the development of smart cities. It is their right measures to the exhaustion of urban resources that promote the emergence of smart cities. Last but not least, the support of technology. On the one hand, the use of solar power and the invention of low-power products have eased the pressure. Water purification projects relieve water pressure.On the other hand, the emergence of Internet of things realizes the connection between the physical world and the network world. Through development of information technology , management and operation of smart cities are in order.\ That is all.