Carbon nanotubes, which have attracted a significant amount of research attention in recent years, are promising nanoscale materials as building blocks for "bottom-up" assembly of nanoelectronics and nanosensing devices. So far, the fabrication of nanotube devices has often been based on randomly growing or depositing nanotubes, and subsequently finding the ones with desired origin and direction using microscopy techniques. However, it is crucial to be able to assemble such devices in a controllable way, in order to study a large number of them systematically. In this paper, I will present our efforts to tackle this assembly problem by using physics and engineering to control the chemistry of nanotube growth. In particular, we have aligned single-walled carbon nanotubes on oxide surfaces by applying an in situ electric field across microfabricated electrodes during chemical vapor deposition growth. We have then extended this technique to two-dimensional assembly of carbon nanotubes. In particular, we have designed an electrode configuration that would give nanotube crosses in a single growth step. Using this design, we have demonstrated the feasibility of 2D assembly of carbon nanotubes using electric field engineering. These experiments also provide invaluable information about how nanotubes respond to the direction, magnitude, and polarity of external electric fields that may be present during growth. The generality, versatility, and scalability of this assembly technique make it very attractive for controlled growth and assembly of nanoelectronics and nanosensing devices.