Hay
From Memory Alpha, the free Star Trek reference
Hay is grass that has been cut, dried, stored, and used for animal feed. Hay is sometimes stored in stacks, referred to as haystacks.
The idiom "needle in a haystack" refers to something being difficult to find or do. Miles O'Brien would occasionally use the term, as did Jadzia Dax once. (DS9: "Battle Lines", "Whispers", "Blaze of Glory")
Data and Artim played in haystacks on the planet Ba'ku before the USS Enterprise-E crew told Data it was time to leave. (Star Trek: Insurrection)
