  We present evidence that the star-forming region NGC 346/N66 in the Small
Magellanic Cloud is the product of hierarchical star formation, probably from
more than one star formation event. We investigate the spatial distribution and
clustering behavior of the pre-main sequence (PMS) stellar population in the
region, using data obtained with Hubble Space Telescope's Advanced Camera for
Surveys. By applying the nearest neighbor and minimum spanning tree methods on
the rich sample of PMS stars previously discovered in the region we identify
ten individual PMS clusters in the area and quantify their structures. The
clusters show a wide range of morphologies from hierarchical multi-peak
configurations to centrally condensed clusters. However, only about 40 per cent
of the PMS stars belong to the identified clusters. The central association NGC
346 is identified as the largest stellar concentration, which cannot be
resolved into subclusters. Several PMS clusters are aligned along filaments of
higher stellar density pointing away from the central part of the region. The
PMS density peaks in the association coincide with the peaks of [OIII] and 8
micron emission. While more massive stars seem to be concentrated in the
central association when considering the entire area, we find no evidence for
mass segregation within the system itself.
