Abstract: Calculators, once occupied a whole room, now fit inside a wrist watch. A similar trend exists in biochemical engineering. Processes involving fluids, which are often performed in large scales, are integrated into micro/nano-scale devices. Such devices, in general called lab-on-a-chip devices, offer a higher accuracy and better efficiency compared to bulk devices.In microfluidic technology fluids are handled in microchannels or as droplets on open surfaces. Nanofluidics is a sister field of microfluidics, and involves manipulation of fluids in nanochannels. Thanks to the recent developments in these fields, micro- and nanofluidics have become the cynosure of point-of-care diagnostics and various applications in bio-chemical engineering. In this seminar I will take you through some interesting research themes in micro-and nanofluidics, which I performed during my PhD and postdoctoral studies. They include both fundamental and applied aspects. In short, we performed cyclic oxidation and reduction of molecules in nanogap sensors -a set of two platinum electrodes separated by a few tens of nanometers. Using these nanogap sensors, we have shown, for the first time, electric detection of single molecules. This technique can make revolutionary changes in DNA sequencing. We further studied the stochastic number fluctuations of the molecules in the nanogap sensors, which led to many fundamental understanding of molecular dynamics in nanofluidic systems.