Picard: 15 ESSENTIAL Star Trek Episodes To Watch First (And Why)
12. "The Offspring" (TNG - Season 3, Episode 16)
Depending on where you stand on certain theories about Picard, "The Offspring" could be extremely relevant to the show or just a little. But it's still probably a key one to watch, especially as it explores more of Data's humanity and how advances in android technology that far back could reveal the truth of precisely what Dahj is.
In the episode, Data uses newly learned information on AI to build himself a child - Lal - to further his journey to humanity and belonging. Naturally, Picard reports her existence to Starfleet and they seek to remove her for study, which Picard once more fights against.
Aside from the android rights issue, this could also be a way to explain the theory that Dahj is Lal - or at least that her neural net (which Data downloaded when she died) is the basis for Dahj. That, of course, assumes she is an android (or at least PART android) though, but even without that, it's an important episode to watch.