Creating a high-quality dataset is a crucial part of any machine learning project. This is even more the case for highly specialized domains such as medicine. In practice, data annotation often takes longer than the actual training and optimization of the models. Medical data annotation includes several process steps: planning, anonymization, provision of the data, annotation/segmentation, and quality assurance. Annotation Lab Essen, an organizational unit of the Institute for AI in Medicine and part of Essen University Hospital, benefits from the highest medical expertise and specializes in the annotation of medical data (images, text and beyond).