This is the last of a series of lectures presented by the German Nobel Laureate Werner Forssmann at the Lindau Meetings. Except for the first lecture, which he delivered in 1957 and which was related to his Nobel Lecture, all his lectures are on more general topics chosen to be important for the education of young medical doctors. As far as I know, this is exceptional at the Lindau Meetings, but there is a good reason. When he was a young doctor himself, Werner Forssmann had the idea of performing heart catheterization, i.e. of bringing a thin rubber tube into a blood vessel and up to the heart to measure the blood pressure there. He wanted to perform the experiment on a patient at the hospital where he was working, but the doctor in charge said no, the experiment would be too risky. But Forssmann successfully performed the experiment on himself in front of an X-ray machine and promptly got fired! So instead of a career in science he began to practice medicine as a profession. In 1956, when the telephone call from Stockholm came, he commented on becoming a Nobel Laureate that “you must have a strong heart to survive being elevated to a fix star on the sky”. So his lectures are really pedagogical and historical overviews meant to be appreciated by young people entering the same career of practising medicine as Werner Forssmann himself once chose.