Most of us have been told by a friend that we have a doppelganger - some stranger they passed on the street who bore an uncanny resemblance to you. But imagine if you could create your very own twin, an exact copy of yourself, but one that lived a purely digital life? We are living in an age where everything that exists in the real world is being replicated digitally - our cities, our cars, our homes, and even ourselves. And just like the hugely-hyped metaverse - plans for a virtual, digital world where an avatar of yourself would walk around - digital twins have become a new, talked-about tech trend. A digital twin is an exact replica of something in the physical world, but with a unique mission - to help improve, or in some other way provide feedback to, the real-life version. Initially such twins were just sophisticated 3D computer models, but artificial intelligence (AI) combined with the internet of things - which uses sensors to connect physical things to the network - have meant that you can now build something digitally that is constantly learning from and helping improve the real counterpart. Technology analyst Rob Enderle believes that we will have the first versions of thinking human digital twins "before the end of the decade". "The emergence of these will need a huge amount of thought and ethical consideration, because a thinking replica of ourselves could be incredibly useful to employers," he says. "What happens if your company creates a digital twin of you, and says 'hey, you've got this digital twin who we pay no salary to, so why are we still employing you?'? Mr Enderle thinks that ownership of such digital twins will become one of the defining questions of the impending metaverse era. We have already started the journey towards human twinning - in the form of the above mentioned avatars - but these are currently rather clunky and primitive. In Meta's (formerly Facebook) virtual reality platform, Horizon Worlds, for example, you may be able to give your avatar a similar face to your own, but you can't even provide it with any legs because the technology is at such early stages. Prof Sandra Wachter, a senior research fellow in AI at Oxford University, understands the appeal of creating digital twins of humans, "it is reminiscent of exciting science fiction novels, and at the moment that is the stage where it is at". She adds that whether someone will "be successful at law school, get sick, or commit a crime - will depend on the still debated 'nature versus nurture question'. It will depend on good luck and bad luck, friends, family, their socio-economic background and environment, and of course their personal choices." However, she explains, AI is not yet good at predicting these "single social events, due to their inherent complexity. And so, we have a long ways to go until we can understand and model a person's life from beginning to end, assuming that is ever possible." Instead, it is in the fields of product design, distribution and urban planning where the use of digital twins is currently the most sophisticated and extensive. In Formula One racing, the McLaren and Red Bull teams use digital twins of their race cars. Meanwhile, delivery giant, DHL, is creating a digital map of its warehouse and supply chains to allow it to be more efficient. And increasingly our cities are being replicated in the digital world; Shanghai and Singapore both have digital twins, set up to help improve the design and operations of buildings, transport systems and streets. In Singapore, one of the tasks of its digital twin is to help find new ways for people to navigate, avoiding areas of pollution. Other places use the technology to suggest where to build new infrastructure such as underground lines. And new cities in the Middle East are being built simultaneously in the real world and the digital. French software company, Dassault Systemes, says it is now seeing interest from thousands of firms for its digital twins technology. So far its work has included using digital twins to help a hair care firm digitally design more sustainable shampoo bottles, instead of endless real-life prototyping. This cuts down on waste. And it is enabling other firms to design new futuristic projects - from jetpacks, to motorbikes that have floating wheels, and even flying cars. Each has a physical prototype too, but the refining of that initial model happens in the digital space.But the real value seen in digital twins is in healthcare. Dassault Systemes' Living Heart project has created an accurate virtual model of the a human heart that can be tested and analysed, allowing surgeons to play out a series of "what if" scenarios for the organ, using various procedures and medical devices.