Microfluidic devices and methods of forming cell reactors for performing cell analysis in a microfluidic chip. A microfluidic chip, in one implementation, includes a plurality of trapping sites, each of the plurality of trapping sites having a plurality of micropillars configured to trap one or more cells in an interior space formed by the plurality of micropillars. The plurality of micropillars in each trapping site form a picoreactor for cell and molecular diagnostics, such as characterizing, isolation, processing, and amplification of different cells, cells containing different substances, different particles, different biochemical compositions, proteins, and enzymes.