The physical appearance of open clusters reflects the underlying star formation process and is a consequence of their dynamic evolution. Many young clusters or groups of stars exhibit a filamentary morphology, which is a heritage of the elongated shape of the molecular clouds in which they form. Conversely, older clusters display extended spatial structures, which are caused by the interplay of internal dynamical evolution and the external Galactic tidal field, resulting in tidal tails. In this talk, I will present the three-dimensional morphology of open clusters in the solar neighborhood based on observational data from Gaia EDR3, DR3. The morphology is quantified using an ellipsoid, and we find that the elongated direction of clusters with tidal tails aligns with the Galactic plane. Our results support the hierarchical star formation model in the solar neighborhood based on the spatial and kinetic characteristics of the young stellar groups. N-body simulations are utilized to compare the observations and quantify the initial conditions during the formation of open clusters. Furthermore, we use simulations to predict the future evolutionary trends of binary clusters and hierarchical young stellar groups.
