This is an important question and, of course, there is always fundamental scientific curiosity. While this is not to be minimized in graduate chemistry research, especially when we are developing new synthetic methods, one might also ask "what are nitrides good for?" To begin our answer, we note that there are many important uses of binary nitrides. These include GaN (the basis of the blue LEDs of the blu-ray player in your Playstation 3, high speed and power electronics), AlN (high thermal conductivity substrates), Si₃N₄ (CVD coating on electronics etc.), TiN and TaN (metallic conductors and diffusion barriers in electronics, colored surfaces in jewelery, artistic displays, etc.) NbN (thin film superconducting devices)  etc. If we look at oxide chemistry it becomes apparent that ternary and quaternary oxides offer a greater, more tunable, qualitatively different and more useful set of properties than the binaries alone. So we believe that it is reasonable to expect that ternary and quaternary nitrides will eventually provide the same, because so many useful binary nitrides are known and because we have already found structurally interesting compounds, indeed some with unusual properties. However, the study of such ternary and quaternary nitrides is still in its infancy, especially when compared to the family of oxides, or even to sulphides, phosphides, carbides etc. We have so much more to learn and that is one reason why we think that nitrides are scientifically exciting as well as being potentially technologically very interesting and useful.