Advances in sub-micron lithograpy have opened the door to the study of the physics of the "mesoscopic" size regime. This regime is characterized by quantum-interference effects enhanced electrical conductance is extremely sensitive to the microscopic impurity potential, hence careful conductance measurements can be used to detect the motions of single atoms. Conductance measurements will be used to study defects in metals and their relation to l/f noise, and tunneling systems in metallic glasses. Our understanding in both of these areas has been limited by our inability to observe the microscopic samples. By measuring conductance fluctuations in submicron samples as a function of sample size, temperature and strain, and of the applied magnetic field, one will probe the properties of individual defects and tunneling systems, as well as their interactions with each other and with the conduction electrons.
