Finishing פרק י"ד, the פריערדיקער רבי explains this phenomenon of the אור extending itself into even the lowest of levels and yet retaining its essence of being אין סוף.

We explore this identity of "אור אין סוף", as well as the contrast of אור and כח, and the example of the light shining through the colored glass, as illuminated by the רבי in תשכ"ד.

The punchline of this פרק is - being that this אור אין סוף exists even within the lowest and lowliest of levels, it is our עבודה to reveal it, expressing Hashem's Essential Existence within our world and our reality!