We have demonstrated a fully integrated, in-plane, single-layer flow cytometry chip device. The device includes fluidic components—a three-dimensional (3D) hydrodynamic focusing geometry based on the “microfluidic drifting” technique developed by our group, and a series of integrated optical fibers to allow the introduction of laser light and on-chip detection of various optical signals such as forward scattering (FSC), side scattering (SSC), and fluorescence. The “microfluidic drifting” technique and integrated optical fibers allow the entire device to be realized in a single, planar layout, which significantly reduces the device fabrication complexity and cost. The device was tested with a series of standard flow cytometry beads of difference size and fluorescent dye concentration.