  We introduce an Active Vertex Model (AVM) for cell-resolution studies of the
mechanics of confluent epithelial tissues consisting of tens of thousands of
cells, with a level of detail inaccessible to similar methods. The AVM combines
the Vertex Model for confluent epithelial tissues with active matter dynamics.
This introduces a natural description of the cell motion and accounts for
motion patterns observed on multiple scales. Furthermore, cell contacts are
generated dynamically from positions of cell centres. This not only enables
efficient numerical implementation, but provides a natural description of the
T1 transition events responsible for local tissue rearrangements. The AVM also
includes cell alignment, cell-specific mechanical properties, cell growth,
division and apoptosis. In addition, the AVM introduces a flexible, dynamically
changing boundary of the epithelial sheet allowing for studies of phenomena
such as the fingering instability or wound healing. We illustrate these
capabilities with a number of case studies.
