Abstract: Determining the quantum ballistic conductance of a nanosystem has become of primary interest in recent years for the promise of novel technological applications for nanoscale quantum electronic devices. In particular, on the theoretical side, a fully first principle theory of electronic transport is highly desirable. In this talk I will discuss recent advances in the development of efficient techniques to compute quantum conductance from first principles and show examples of prototypical applications, ranging from atomic chains to carbon nanotubes and nanotube assemblies.