A rare element only found on a few planets in the galaxy. The element emits a radiation that can remove the telepathic abilities from a telepath that is exposed to it. If spread around the galaxy with a Photonic explosion it could remove the telepathic abilities from every creature in the galaxy. The Galactic Federation has concealed the location of any sources of Barlumin to such a degree that most people believed it did not exist. The Kulthan found a seam on Earth near Loch Ness.

A gun that can be used to remove the telepathic abilties from a telepath. It contains Barlumin and can project a Barlumin ray over several metres. 

The Sorsons gave the American President a Barluminite Ray Gun after they landed on Earth. The President used it to capture Mike and Hsui Tai.

The process a person goes through when they become one of the Tomorrow People. A telepath can not normally use their telepathic abilities until they reach their early 'teens. 

The Tomorrow People often become awayre that someone is breaking-out when they develop telepathy. This is usually very painful and can be fatal. It manifests itself in a flood of telepathic thoughts from the Saps around them, and the attempts at communication from the Tomorrow People. If the Tomorrow People do not reach them in time they can die due to the exstream strain it places on their body. If they develop teleporting too quickly they can be stranded in Hyperspace. Carol helped Stephen to break-out (see transcript). 

Sometimes other abilities develop first, for example telekinesis. When some has broken-out, it takes sometime for them to learn how to use the various abilities.

A strange fabric called Bubble Skin, that has been made into a jump suit. When worn the material attaches itself to the skin of the wearer. The jump suit is actually an alien parasite called a Ballboid. When the jump suit is worn the Ballboid controls the wearer.