Figure 3.

Branching strategies. Organ branching can be dissected into a few basic strategies. None of the branching events described in this review follow one single scheme but, rather, a combination of them. However, the identification within each organ of these prime processes can help us to understand and experimentally examine their development. (A) Migration toward a signaling source (green). (B) Migration toward a signaling source (green) constrained by repulsive signals (red block-arrows) or physical obstacles (blue). (C) Migration following an underlying patterned structure (purple stripes). (D) Intussusception: splitting of a branch into finer branches.