  We demonstrate with experiments and simulations how microscopic
self-propelled particles navigate through environments presenting complex
spatial features, which mimic the conditions inside cells, living organisms and
future lab-on-a-chip devices. In particular, we show that, in the presence of
periodic obstacles, microswimmers can steer even perpendicularly to an applied
force. Since such behaviour is very sensitive to the details of their specific
swimming style, it can be employed to develop advanced sorting, classification
and dialysis techniques.
