Coalescence or fusion of cellular clusters is essential in embryonic development and tissue engineering. Previous works in this field often use a highly approximate theory of viscous sintering from the '40s as the basis for measurement and comparison. However, there are numerous unique features that distinguish cellular aggregates from other squishy soft matter systems. For example, will the unique interactions independent of distance but dependent on neighboring relations, which can be simulated with the vertex model or Voronoi model, influence the dynamics of coalescence? We need new theories for cellular clusters!

In collective cell migration, each cell's polarization is coordinated by its neighbors through chemical or mechanical communications. For example, some cells can adjust directionality and speed relative to their neighbors; others are integrated into supracellular arrangements, with marked front-to-back specialization and continuity
of cytoskeletal structures between neighboring cells. The coordination mechanism, which can promote the group's overall efficiency in different aspects, is one focus in collective cell migration.

The ability to move efficiently, in the right direction, or in an orchestrated collective manner, is essential for organisms as simple as bacteria in survival and as complex as mammals in wound healing, embryonic development, etc. Cells depend on delicate signaling pathways to make the proper decisions, while defects in the signaling mechanism might result in severe diseases and even death.