All Bachelor's programmes offer 15-30 EC space for minor programmes. The first semester of the third year is designated as a minor and exchange semester. You can, for instance, follow the Education minor or the minor in computing science during that semester.
You may also put together a series of related courses (e.g. on economy, or on nano science, or on mathematics). You must get approval from the examination board to incorporate this minor in your programme.
Doing a minor programme will reduce the number of specialisation courses you will have to do. It will give you the possibility of looking beyond your own field. Some information on minor programmes can be found in the minor prospectus.