A 32nd-century material made of tiny particles that can be ordered into almost any shape or function, used for consoles, tools, furniture, ship hulls and repairs.
Programmable matter is the signature technology of the far future in Star Trek: Discovery. It appears as a cloud of dark particles that flows together into a solid object and adapts to its user. Book's ship is largely made of it and changes form in flight.
The crew of the USS Discovery meet it in the third season. When the ship is refitted at Federation Headquarters in Scavengers, its consoles and controls are replaced with programmable matter, and the crew have to learn interfaces that mould themselves to the user.
It can also be used for emergency repairs and medical work. The technology returns in Star Trek: Starfleet Academy, where Caleb Mir uses programmable matter to restore life support aboard the derelict USS Miyazaki in Come, Let's Away.