In case you didn't see any of the various media coverage, someone 3D-printed a metal gun. There is nothing you should be more worried about than that, except for literally everything else in the universe.
The company that pulled off the feat is called "Solid Concepts" and, as is the tradition in the DIY gun space, apparently, created a video about the weapon's construction. The science blog Phys.org describes the construction:
In this case, the printer uses what is known as a direct metal laser sintering (DMLS) process—metal powder is heated to create a type of ink that can be used for printing. ... The newly printed gun, created using blueprints of a real handgun formerly used by the US military, was made by printing almost all of the parts—it was finished by assembling by hand. No machining was necessary, just some hand tooling.
You may remember that when Defense Distributed released plans for a 3D-printable weapon online earlier this year, we tried to get someone to print one for us and then tried printing it ourselves. Allow us to summarize our experience: The idea that anyone besides dedicated hobbyists would be able to easily construct a weapon using a home 3D-printer is optimistic. And even if they did, they'd still need a bullet.
But what the Solid Concepts achievement tells us is this: For those with the capability to conduct high quality construction using expensive manufacturing devices, creating these guns is now a reality. You know who has expensive manufacturing devices and high quality construction? Gun companies. Getting freaked out by this would be like stumbling into a room at the Glock factory that's mass producing weapons and then fearing that, soon, every kid on every block would be operating gun factories in their basements. This does not scale down.