In the 19th century, Florence Nightingale pointed to the importance of nursing documentation for the care of patients and the necessity of data-based statistics for quality improvement. The same century, John Snow projected his observations about patients with Cholera on a street map, laying the ground for modern epidemiological science. The historical examples demonstrate that proper data are the foundation of relevant information about individuals and of new scientific evidence. In the ideal case of Ackoff's pyramid, information, knowledge, understanding, and wisdom arise from data.