From its origin to its death the human organism is submitted to functional, material, and morphological changes that are perceptible. These changes permit classifying an individual as young, adult, old, active or infirm. But this estimation is not always correct. Some appear younger, some older than expected from their chronological age. But what is aging and how can it be measured? For this, so-called markers or biological markers of aging are used which are measurable indicators of aging in live organisms. A description of the complexity, the asynchronous course, and the biological variety and variability of biological age is less successful with a single indicator than with the inclusion of several markers in a multi-factorial measuring system, in a so-called test battery. Various test batteries have already been applied in numerous studies that consist of biochemical scans, mental and also social parameters in different combinations. A more precise description of such a test battery can be seen in the following example of a discussion of the ILSE study.