Although egg cells are visible to the naked eye, the history of cell biology is closely coupled to that of microscopy. In nearly 350 years, cell research has produced an extraordinary rich panorama of studies, concepts and representations. Robert Hooke's 1665 analogy to monk cells, the transition from ‘cellular tissue’ to single ‘cells’ around the year 1800, Schleiden and Schwann's identification of the cell as the elementary unit of life, the prominent status it gained during cytology's expansion to the other fields of biomedical inquiry, Schultze's definition as ‘a clump of protoplasm containing a nucleus’, the worlds of endocellular and ultrastructural organization, the ‘compartimentalization’ of the cell in the 1950s and 1960s, its role as map for biochemical and molecular research, all these are just few of the many historical answers to the question ‘what is a cell and what is it good for?’.

Key concepts:

• For the beginning of cell biology as a new research field it was not sufficient to be merely able to see cells.
  
• The development of cell biology was coupled with the evolution of optical instruments and of anatomical theory.
  
• One indispensable prerequisite for the formulation of the first cell theory was the shift from the concept of cellular tissue to that of cells as single units.
  
• Cell research underwent ‘golden ages’ whenever cells were considered the basic units of life.
  
• Many outstanding life scientists did not attribute central importance to cells.
  
• The study of cells was (and still is) extraordinarily rich in different ways of seeing, describing, depicting and conceiving.
  
• Though it originated from a specific theory, the history of cell biology is characterized by its growing independence from general theory.
  
• Throughout its history cell biology was characterized by its ability to expand into neighbouring research fields and to integrate their concepts and methods.