The present disclosure is drawn to microfluidic devices. A microfluidic device can include a substrate, a lid mounted to the substrate, and a microchip mounted to the substrate. The lid mounted to the substrate can form a discrete microfluidic chamber between structures including an interior surface of the lid and a portion of the substrate. The lid can include an inlet and a vent positioned relative to one another to facilitate loading of fluid to the discrete microfluidic chamber via capillary action. A portion of the microchip can be positioned within the discrete microfluidic chamber.