Which parts of the body can we 3D print?

While not quite as complex as a real human brain, scientists are moving closer to constructing the complex tissue. Using a handheld 3D printer, researchers at ARC Centre of Excellence for Electromaterials Science in Australia developed a method for constructing layered biological structures that closely resemble cerebral cortex tissue.

“We are still a long way from printing a brain but the ability to arrange cells so as they form neuronal networks is a significant step forward,” Professor Wallace said in a statement.

Though they don’t come filled with marrow, doctors, scientists, and law enforcement are finding 3-D printers useful for replicating bone.

In 2014, doctors in the Netherlands reported that they successfully replaced most of a human’s skull with a 3-D printed plastic one for the first time. The same year, a surgeon in Newcastle used 3-D printing to manufacture a new pelvis for a man who had lost half his original one to cancer.

In addition, law enforcement and forensic anthropologists have increasingly relied on 3-D scanning and printing to bring bone evidence in front of juries and to convict criminals. It has also made a great way for scientists around the world to study fossils.

There has been increased interest in printing spines recently. In July, the German company joimax received FDA approval to sell its EndoLIF On-Cage, which offers “minimally invasive… alternative for fusion in the lumbar spine.” Then in the same month, Oxford Performance Materials also gained FDA approval for its 3-D printed spinal implants.

Scientists have been replicating ears since 2013, and bioengineers at Cornell University were able to use a printer with “injectable gels made of living cells” to create lifelike material for the prosthetic. Princeton scientists found the same year that they could infuse electronic components with a hydrogel similar to other forms of printed biological tissue to create an ear that can actually pick up radio waves.

Last year, the UK-based company Fripp Design and Research announced it would be printing up to 150 prosthetic eyes an hour .

But that is so 2014. Italian researchers at MHOX hope that by 2027 they will be able to create eyes with enhanced vision and WiFi connection. But until then, the researchers will continue working on their line of synthetic eyes for those who need them.

In 2012 – in what doctors called the first operation of its kind – an 83-year-old Netherlandic woman had her jaw replaced by an artificial one. Thanks to the technology and Operation of Hope, another recipient of the man-made jaw was Zimbabwean man who lost the use of his jaw after land mine exploded in his face in his youth.

And what about when you need to fill your jaw with teeth? The latest updates to 3-D printingnow allows dentists to print a tooth in 6.5 minutes.

Tessa Evans, a two-year-old born with an extremely rare medical condition that resulted in her having no nose or sense of smell, is one of many who now have a nose because of 3-D technology. And like with ears, the process for creating the cartilage is only becoming quicker. The material can be pushed out in 16 minutes.

This past April, 2-year-old Hannah Warren – who was born without a trachea – became the youngest patient to ever receive a bioengineered organ, which was made of trache plastic fibers and her own stem cells. In the same month, three infants lives were saved by printed throat implants.

3-D printed prosthetics – whether it be legs, feet, hands, or fingers – have become commonplace. There is even a website where you can get a customized one. The prosthetics are moving on to the next phase of development and getting high tech upgrades, like the one created by OpenBionics, which added NFC capabilities to the fingers of a 3-D printed hand.

Doctors have found that 3-D printing machines are great at manufacturing items that are a perfect fit for patients; especially for something as oddly shaped as joints.

Researchers from Texas Tech University were able to utilize 3-D printing to create “extremely tough hydrogel” that could be used to make load-bearing body parts such, as knee cartilage, and reduce the need for joint replacements with things like sports injuries.

At Charing Cross Hospital in London, the medical staff is incorporating 3-D technology into much of what they do. “Bone shape and size can vary widely between individuals and we provide the 3D-printed parts that are an exact fit,” Dr. Susannah Clarke told The Telegraph. “This reduces costs and inefficiencies.”

While this printed object may be more glamour than revolutionary, they certainly look really cool. Clawz, a Shanghai-based startup, designs and manufactures a wide variety of 3D-printed press-on nails that can be ordered in different textures or metallics. TheLazerGirls also offer some funky designs that are sure to get any passer-by’s attention.

Animal testing has always had a slight moral ambiguity to it, but 3-D printing is opening up opportunities to stop testing on animals and humans alike. L’Oreal has been working with Organovo to create what it calls Episkin, which is made from incubated skin cells donated by surgery patients. With further experimentation, the skin could even one day be printed for burn victims.

This may seem like an odd thing to attempt to print, but it is essential to assuring that more complex 3-D printed organs can function properly. Fraunhofer Institute and the ArtiVasc 3D project recently unveiled their breakthrough discoveries in bioprinting artificial blood vessels. ArtiVasc 3D’s missions is to focus on “developing standardized processes for scaffold production and to cultivate vascularized skin rapidly and inexpensively.”

Possibly even more impressive is that these printers can even create cells. Researchers from Ulsan National Institute of Science and Technology developed a new, very tiny high-resolution 3-D printer that layers special inks to form microscopic 3-D models, some even smaller than red blood cells.

While we can’t print nerves (yet), scientists have figured out how to at least spur regrowth and reconnection in damaged ones.

In a paper titled, “3D Printed Anatomical Nerve Regeneration Pathways” researchers found that a tiny, three-pronged 3-D printed structure could guide nevers back to their proper place.Xiaofeng Jia, a professor of neurosurgery at the University of Maryland who worked on the project, told MIT Technology Review that this should be thought of as a starting point that “opens the door” to make more complex versions of implants for regeneration.

In what seems like something straight out of Dr. Frankenstein’s lab, researchers have figured out how to create beating 3-D printed hearts. But the artificial organs have also been printed in plastic or rubber forms that have saved numerous individuals.

In what was called a first of its kind surgery, researchers at Kyoto University used 3-D printers to help surgeons complete a living donor lung transplant on a Japanese woman last year. While printing a full set of lungs is still years away, as the Lung Institute points out, the advancement of bioprinting could one day aid those suffering with lung disease.

The liver is another organ that the technology almost has down. Organovo, a bioprinting company, recently began selling liver tissue to pharmaceutical laboratories to use in early-stage drug testing. While the company can print everything from bone to blood vessels to heart tissue, it hopes to one day produce entire organs that could be implanted in humans.

These advancements also helped doctors in China used 3-D imaging to recreate a man’s tumorthat was wrapped around his liver, allowing them to cut out 42.8% compared to 70%, which likely would have led to liver failure.

In 2013, scientists unlocked the possibilities of printing kidneys and were able to create miniature, living ones. Unfortunately, Chinese doctors were only able to keep them alive for four months.

This year, Organovo showed off its new technique for 3-D printing human kidney tissue at the 2015 Experimental Biology conference in Boston.

Bladders – a simple, hollow organ – have been artificially created in labs and implanted in patients since 1999. Wake Forest Institute for Regenerative Medicine has been at the forefront of bioprinting – assisting in advancing the creation of heart cells, kidneys, and skin – and Anthony Atala, the institute’s director, has been swapping the organ with engineered ones for years.

Intestines are another complex organ that still has a ways to go, but bioengineers are getting closer.

In 2011, John March, a biological and environmental engineering assistant professor at Cornell, began collaborating with David Hackam, a Pittsburgh-based pediatric surgeon, on a small artificial intestine using collagen and stem cells. The following year, EPFL researchers in Switzerland created the “NutriChip,” a miniature “on-chip gastrointestinal tract in order to observe the effects of various nutrients on health.” Scientists at Harvard’s Wyss Institute were also able to create a “gut-on-a chip,” which used intestinal cells in a tiny silicon polymer device to mimic the real thing.

Most recently, a team at University of Texas’ Medical Branch at Galveston presented their findings at the 2015 Digestive Disease Week, where they “demonstrated for the first time the ability to create fully functioning “bio-artificial” tissue grown from intestinal stem cells in the bowels of laboratory rats.”

Publication does not imply endorsement of views by the World Economic Forum.

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Author: Tess Danielson is the tech intern at Business Insider.

Image: Combination picture of a spine model, a spine model implanted with a traditionally used titanium tube, and a spine model implanted with a 3D-printed artificial axis (L-R), are displayed at Peking University Third Hospital in Beijing. REUTERS/Jason Lee