  In this work we study the internal spatial structure of 16 open clusters in
the Milky Way spanning a wide range of ages. For this, we use the minimum
spanning tree method (the Q parameter, which enables one to classify the star
distribution as either radially or fractally clustered), King profile fitting,
and the correlation dimension (Dc) for those clusters with fractal patterns. On
average, clusters with fractal-like structure are younger than those exhibiting
radial star density profiles. There is a significant correlation between Q and
the cluster age measured in crossing time units. For fractal clusters there is
a significant correlation between the fractal dimension and age. These results
support the idea that stars in new-born clusters likely follow the fractal
patterns of their parent molecular clouds, and eventually evolve toward more
centrally concentrated structures. However, there can exist stellar clusters as
old as 100 Myr that have not totally destroyed their fractal structure.
Finally, we have found the intriguing result that the lowest fractal dimensions
obtained for the open clusters seem to be considerably smaller than the average
value measured in galactic molecular cloud complexes.
