Microfluiclic and lab-on-a-chip devices have attracted widespread interest in separation sciences and bioanalysis. Recent designs in microfluidic devices extend common separation concepts by exploiting new phenomena for molecular dynamics on a length scale of 10 mu m and below, giving rise to novel manipulation tools and nonintuitive phenomena for microseparations. Here, we focus on three very recent developments for bioseparations based on tailored microfluidic systems: Single cell navigation, trapping and steering with subsequent on-chip lysis, protein separation and LIF detection (Section 3.1), then we report dielectrophoretic trapping and separation of large DNA fragments in structured microfluidic devices (Section 3.2). Finally, a paradoxial migration phenomenon based on thermal fluctuations, periodically arranged microchannels and a biased alternating current electric field is presented in Section 3.3.