With the emergence of scientific understanding based on observation and experimentation, the 17th century also saw the need for craftsmanship at the university. Scientists now used instruments to observe, measure and analyse data that must be designed, repaired and maintained. The construction and execution of experiments also required many helpers and skilled hands. Then, as is now, the real scientific significance of the work of craftsmen, technicians or laboratory assistants does not correspond to their official representation. In publications, they may, if at all, get a mention as a side note and in photographs, where scientists are represented in their working environment, they remain mostly invisible.