  Despite the spectacular achievements of molecular biology in the second half
of the twentieth century and the crucial advances it permitted in cancer
research, the fight against cancer has brought some disillusions. It is
nowadays more and more apparent that getting a global picture of the very
diverse and interlinked aspects of cancer development necessitates, in synergy
with these achievements, other perspectives and investigating tools. In this
undertaking, multidisciplinary approaches that include quantitative sciences in
general and physics in particular play a crucial role. This `focus on'
collection contains 19 articles representative of the diversity and
state-of-the-art of the contributions that physics can bring to the field of
cancer research.
