Chapter 30 covers medicaments, human blood, vaccines, dressings and pharmaceutical articles. The molecule alone is not enough: a pure active substance stays in Chapter 28 or 29 until it is put up in measured doses or packed for retail sale.
That switch is what makes the chapter. Heading 3004 requires a dosage form — tablet, ampoule, measured dose — or retail packing. In the other direction, a food supplement belongs to Chapter 21 and a cosmetic to Chapter 33, even when either carries a health claim.
Every number opens on the lines beneath it, down to the ten-digit classification number.