In the early 1970s PEX were being developed in order to produce energetic compounds with a toothpaste-like consistency so that the PEX could be moved into position when arming the warhead. In the late 1990s development work was conducted on PEX for the filling of small-volume microdevices such as micro-actuators. More recently Cranfield University has just begun research into the development of SPEX. This review outlines the developments in high explosive pastes and concludes with future developments in PEX.