Cosmological inflation generates primordial density perturbations on all scales, including those far
too small to contribute to the cosmic microwave background. At these scales, isolated ultracompact
minihalos of dark matter can form well before standard structure formation, if the perturbations
have sufficient amplitude. Minihalos affect pulsar timing data and are potentially bright sources of
gamma rays. The resulting constraints significantly extend the observable window of inflation in
the presence of cold dark matter, coupling two of the key problems in modern cosmology.