Described here is a novel microelectronic / microfluidic hybrid system that can control the motion of individual biological cells in fluids with microscopic resolution. The hybrid system starts with a microelectronic chip produced in a foundry using standard microfabrication techniques. A microfluidic channel is then fabricated on top of the microelectronic chip to provide biocompatible environments. Microelectronic devices actively interact with biological cells through electromagnetic fields to control the motion of individual cells in fluids. The unique combination of microelectronics and microfluidics, hence the new name microelectronic / microfluidic hybrid systems, provides unprecedented capabilities of cell manipulation, enabling researchers to carry out biological experiments in a standardized and repeatable manner.