  Collisions between cold molecules are essential for studying fundamental
aspects of quantum chemistry, and may enable formation of quantum degenerate
molecular matter by evaporative cooling. However, collisions between trapped,
naturally occurring molecules have so far eluded direct observation due to the
low collision rates of dilute samples. We report the first directly observed
collisions between cold, trapped molecules, achieved without the need of laser
cooling. We magnetically capture molecular oxygen in a 0.8K x kB deep
superconducting trap, and set bounds on the ratio between the elastic and
inelastic scattering rates, the key parameter determining the feasibility of
evaporative cooling. We further co-trap and identify collisions between atoms
and molecules, paving the way to studies of cold interspecies collisions in a
magnetic trap.
