For some countries a visa is required when travelling to the Netherlands. Please visit this website for more information: https://www.schengenvisainfo.com/netherlands-visa/
For a VISA application you need an invitation letter, which can be obtained after your registration process has been completed. Contact the conference office of BIOROB2018 firstname.lastname@example.org with your request.
The letter will be sent to you by e-mail as a PDF file.