The use of centralized, curated and quantitative data is becoming increasingly important in today’s biology. The course « Cell biology by the numbers » will highlight the key numbers which describe the lives of the cells and the necessary efforts to provide definitive statements about their value. This course, intended for biologists, will provide participants with the appropriate mathematical tools to apprehend and explore the key numbers of cell biology and many key physico-chemical processes. The course will provide key examples about sizes, concentrations, energies and key quantitites that describe the living world, in both an entertaining and surprising fashion. Practical sessions, dedicated to programming (Python), will be organised every afternoon.