In Medical Informatics three types of processes play a central role: organizational, patient-related and decision making-related processes. The first type deals with settings, such as a hospital care setting or a primary care setting; the second is related to health and disease (i.e. to patients); the third type of process aims at assisting in decision making and therapy and evolves in the brains of healthcare professionals. Hence, in all domains data, information and knowledge play a key role. As these three processes evolve, dealing with individuals – patients, doctors and nurses – because of that human factor there are obviously limitations imposed by formalization and standardization. In the past, there have been some unrealistic expectations regarding the possible contributions of medical informatics to healthcare. However, such contributions appeared to be very modest, to say the least. The same applies to the overly optimistic expectations regarding the introduction of electronic health records. Although the technology is widely available, all these developments appear to be far more complex than expected. The need for an improved understanding of the nature of medical knowledge to better serve health remains to be emphasized.