Punctilious

punctilious \puhnk-TIL-ee-uhs\, adjective:
Strictly attentive to the details of form in action or conduct; precise; exact in the smallest particulars.

Nicholas showed us his butterfly collection. He had done a splendid job of spreading them (better than I ever have, let alone at his age). I tried to impress upon him the need for punctilious labeling, a tedious business that raises a butterfly from a mere curio to a specimen of scientific value.
-- Robert Michael Pyle, ChASINg Monarchs