DimensionalMeshComponents

DimensionalMeshComponents[mr] gives a list {r0,r1,…} of regions such that rd has dimension d for a mesh region mr.

Examples

Get components of different dimensions:

mesh = BoundaryMeshRegion[{{0,0},{1,0},{1,1},{0,1}}, Line[{1,2,3,4,1}]];
DimensionalMeshComponents[mesh]

Extract 1D components:

DimensionalMeshComponents[mesh][[2]]

Please visit the official Wolfram Language Reference for more details.