  The phase space distribution of matter out to $\sim 100 \rm Mpc$ is probed by
two types of observational data: galaxy redshift surveys and peculiar motions
of galaxies. Important information on the process of structure formation and
deviations from standard gravity have been extracted from the accumulating
data.
  The remarkably simple Zel'dovich approximation is the basis for much of our
insight into the dynamics of structure formation and the development of data
analyses methods.
  Progress in the methodology and some recent results is reviewed.
