Self-healing materials can heal damage to enhance stability and lifetimes.Compared with the healing of bulk materials, the healing of films existing on solid substrates is more challenging because the strong binding force from underlying substrates restricts the molecular components migrating across the damaged areas.To achieve this goal, we developed water-enabled healable polyethylenimine (bPEI)/poly(acrylic acid) (PAA) films capable of healing micrometer-sized defects through exponential layer-by-layer (LbL) assembly technique (Figure 1).[1]