The electronic devices have such impact on our lives that it is impossible to imagine our present society without them. Nowadays, the spatial dimensions and working times of the commercial electronic devices are arraying at nanometer and picoseconds scales, so that their performance has to be understood with quantum mechanics. Quantum electron transport theories and their application to electron device modeling have matured into a well-established ?eld with active research, intensive software development, and vast commercial applications. On the other hand, Bohmian mechanics is a well established theory for computing quantum phenomena. Based on this formalism, in this book, a general versatile and time-dependent 3D electron transport simulator for nanoelectronic devices named BITLLES is developed (http://europe.uab.es/bitlles). In particular, the simulator takes advantage of the use of (Bohmian) conditional wavefunctions to tackle, both, the quantum many-body and the quantum sequential measurement problems, which become of fundamental importance to understand the noise and high-frequency behavior of state-of-the-art nanoelectronic devices.