A microfluidic device has at least one microfluidic fluidic flow path, has at least one inlet port, and has at least one optical detection area. The optical detection area is optically coupled to the flow path. The inlet port is coupled to the flow path also. Besides this, the microfluidic device comprises at least one adjusting device. The adjusting device is fixed to the microfluidic device and is adapted for guiding respectively adjusting an optical device relatively to the optical detection area of the microfluidic device.