Molecular separations are extremely important in a wide range of technologies, from conventional proteomics to pathogen detection and DNA fingerprinting. A complication arises from the fact that molecular components in mixtures can span an enormous range of concentration. Conventional approaches such as antibody depletion are not sensitive enough to detect numerous medically significant biomarkers, whose incidence in blood could be as much as a trillion times less abundant than the most plentiful protein, albumin. New research shows a new path in miniaturized molecular separations. It describes a new device that demonstrates simultaneous concentration and separation of proteins by conductivity gradient focusing. Concentration and separation take place in an electric-field-driven 120 nm deep nanochannel that supports a stable salt and conductivity gradient. The results show that relevant proteins can be concentrated to detectable levels.