MIT's Mediated Matter Group develops novel production methods that allow us to shape material in new ways. As part of their Additive Manufacturing of Optically Transparent Glass project, they've developed a 3D printer that can actually handle molten glass.

The FDM-style printer they've developed, called the G3DP, uses a "Kiln Cartridge" to heat the material to 1900 freaking degrees Fahrenheit. As for applications, it's apparently not for the tabletop-sized, vase-like objects you saw in the video; it seems they intend to scale this machine up with the intent of applying it to architecture. As they explain:

[Existing] digital design and construction technologies for product and building scale are generally limited in their capacity to deliver multi-functional building skins…. The Glass Printing project is an enabling technology for optical glass 3D printing at architectural scale designed to manufacture multi-functional glass structures and facade elements.

The final size of the G3DP machine the team is envisioning would thus likely be enormous, on the scale of what China is using to 3D print those houses.