In his 1907 article, "Man's Greatest Achievement", Tesla equates the imperceptible primary substance with the luminiferous aether. It is now suggested that the luminiferous medium, which is the medium for the propagation of light, is in fact perceptible matter, just like ponderable matter, arising when the primary substance is rendered into tiny whirlpools, and that the luminiferous medium differs in nature from ponderable matter, only in scale, in that the former is comprised of leptons.
Article Tesla on the Aether and the Implications