  The largest galaxy systems in the cosmic web are superclusters, overdensity
regions of galaxies, groups, clusters, and filaments. Low-density regions
around superclusters are called basins of attraction or cocoons. In my talk I
discuss the properties of galaxies, groups, and filaments in the A2142
supercluster and its cocoon at redshift $z \approx 0.09$. Cocoon boundaries are
determined by the lowest density regions around the supercluster. We analyse
the structure, dynamical state, connectivity, and galaxy content of the
supercluster, and its high density core with the cluster A2142. We show that
the main body of the supercluster is collapsing, and long filaments which
surround the supercluster are detached from it. Galaxies with very old stellar
populations lie not only in the central parts of clusters and groups in the
supercluster, but also in the poorest groups in the cocoon.
