The आत्मन Ātman is the Self.
आ Ā almost always signifies ब्रह्मन् Brhman, the source.
आत् Āt means coming from the source.
मन Muhn means mind.
So आत्मन Ātman inherits its psychic architecture from ब्रह्मन् Brhman.
Hence the आत्मन Āatman, Self, also realizes it is a conscious being.
Initially the Self appears fragmented in a cloud of disjointed ignorance.
Then through the practice of Yoga these fragments shine forth as facets.
This multi-faceted Self expresses itself brilliantly as a multi-hued crystal reflecting the universal conscious being ब्रह्मन् Brhman.