The psionic matrix emanates from Aiur.
Protoss structures and, to a lesser extent, units, draw their energy from this matrix. While a nexus provides a link to this matrix, khaydarin crystal-based pylons are needed to actually tap into the energy required to provide psionic energy to new colonies. Each pylon generates a short-ranged aura of energy, which can provide the power needed by structures and warp gates. If a protoss building loses its connection to the psionic matrix, it will shut down until it is reconnected, and new units cannot be gated in if there is insufficient psionic energy to provide them with power.