3d Printer are just 3d printer.They are just printers which can print 3d objects.You can print anything what ever the complexity may be.Just like this-
or
You can print anything including shoes,Clothes or even pizza.
3D printers are now in prototype. You can scan anything with the 3D scanner and replicate it with the 3D printer.
Of-course they are not in sale right now but in future you can buy it.There are a lot of 3d printing pens in prototype like the 3doodler.