Surface disorder and structural complexity in 122-type iron pnictide superconductors have long hindered direct access to their intrinsic electronic properties by surface-sensitive probes. Here, I present our recent progress in atomic-scale control and characterizations of 122-type iron pnictide films and heterostructures, achieved via the combined use of molecular beam epitaxy, scanning tunnelling microscopy/spectroscopy and transport measurements. By realizing well-controlled surface terminations, we directly visualize atomic-scale electronic nematicity and charge order on the FeAs plane and uncover intrinsic, nodeless superconducting gaps through engineered BaAs/FeAs heterostructures. Tunnelling spectroscopy at magnetic vortex cores reveals unconventional bound states, indicative of intertwined topology and charge order. Coupled with the artificial building of FeAs-based interface superconductors, these results establish a versatile platform for disentangling and controlling the interplay between nematicity, unconventional superconductivity, and nontrivial topology in iron pnictide superconductors.