As Nanobiology is a joint program, offered by TU Delft and Erasmus University/Erasmus MC, Open Days are held on both locations. The Open Days are open to 4/5/6 vwo and are essentially the same, so you can visit either location.
EUR: For more information and dates, please see the EUR site.
TU Delft: For more information and dates, please see the TU Delft site.