Before the commencement of the courses of each semester, every student has to fill in a form, stating which courses s/he wishes to attend. Courses are Compulsory (Required or Core), Elective Compulsory and Optional (Options). On the one hand, compulsory courses aim at providing students with a basic, solid scientific background, which is considered necessary for their specialisation and training. On the other hand, the elective compulsory courses aspire after deepening the knowledge of the respective discipline and after making students familiar with research methodology. The student can choose particular elective compulsory courses either freely or from particular categories of courses offered by the different thematic areas of the respective Undergraduate Studies Programmes. Lots of these courses require the successful completion of the corresponding compulsory courses; that is, they have prerequisites. Finally, Options give the student the opportunity to attend and study subjects tallying with his/her own personal interests.