  The various mechanisms of magneto-convective energy transport determines the
structure of sunspots and active regions. We characterise the appearance of
light bridges and other fine-structure details and elaborate on their
magneto-convective nature. We present speckle-reconstructed images taken with
the broad-band imager at the 1.5 m GREGOR telescope in the 486nm and 589nm
bands. We estimate the spatial resolution from the noise characteristics of the
image bursts and obtain 0.08" at 589nm. We describe structure details in
individual best images as well as the temporal evolution of selected features.
We find branched dark lanes extending along thin (~1") light bridges in
sunspots at various heliocentric angles. In thick (~2") light bridges the
branches are disconnected from the central lane and have a Y shape with a
bright grain toward the umbra. The images reveal that light bridges exist on
varying intensity levels and that their small-scale features evolve on
timescales of minutes. Faint light bridges show dark lanes outlined by the
surrounding bright features. Dark lanes are very common and are also found in
the boundary of pores. They have a characteristic width of 0.1" or smaller.
Intergranular dark lanes of that width are seen in active region granulation.
While central dark lanes in thin light bridges are elevated and associated with
an density increase above upflows, the dark lane branches correspond to
locations of downflows and are depressed relative to the adjacent bright
plasma. Thick light bridges with central dark lanes show no projection effect.
They have a flat elevated plateau that falls off steeply at the umbral
boundary. There, Y-shaped filaments form as they do in the inner penumbra. This
indicates the presence of inclined magnetic fields, meaning that the umbral
magnetic field is wrapped around the convective light bridge.
