Here we have some text explaining somoething about mathematics.
A vertex-and-edge graph with the set {a, b, c} as a vertex at the top level; The sets {a, b}, {a, c}, and {b, c} at the second level; the three sets {a}, {b}, and {c} at the third level; and the empty set at the fourth level. Lines (edges) indicate which sets are subsets of which other sets.