 By now, you've probably heard of 3D printing. From car parts and plastic toys, to works of art, and even desserts, 3D printing offers endless possibilities in our increasingly DIY world. Perhaps one of the most exciting and promising of these is the ability to print human tissue and organs. It might sound like the stuff of the future, but as highlighted in the August issue of MRS bulletin, the era of 3D bioprinting is here. And if researchers can work together to solve the major challenges facing this rapidly growing field, they could make organ and tissue engineering as easy as pushing a button. By far the greatest challenge in printing living matter is making sure that matter stays alive, both during and after printing. Cells thrive within a narrow range of temperature, pressure and oxygen level, and must remain sterile. Bioprinting experts must therefore ensure that the inside of their devices and, more importantly, the inks that they print with provide a bio-friendly environment. For material scientists, the issue represents an important design problem, giving liquid-loving cells a happy home while making implants strong enough to keep their shape once in the body. Researchers have devised several creative solutions to that problem. For example, using biocompatible polymers, called bio-inks, that gel when squeezed out of a printing nozzle. But many other issues still remain. For one, it's not entirely clear how all the forces felt by bio-inks affect cell survival. Or, for that matter, how cells themselves affect the mechanical and material properties of bio-inks and printed tissue. And then, of course, there's cost. Even when researchers understand these various structure-property relationships, will bioprinting be affordable? Still, a future where organs such as liver, bone and heart can be printed to order may not be far away. The articles gathered in this month's MRS Bulletin take a close look at how researchers are tackling these and other issues as they vie to bring bioprinting into the mainstream. To learn more about the current status and future of 3D bioprinting, register for the MRS on-demand webinar, 3D bioprinting of organs and organs on a chip.