Welcome to the world of the pith
What are pith cells, you ask? Pith is the name for the spongy tissue found right at the centre of many stems, including the hemp stem. Pith cells have a wide variety of functions; they can be metabolically active, can serve as storage cells or can transfer nutrients over short distances. They differ from fibres in that the pith cells have thin walls around them, and do not function primarily in structural support.
This original hemp specimen was hand sectioned and stained with the dye Toluidine blue. Toluidine blue is a metachromatic dye, which means it changes colour depending on the chemistry of the compounds it is staining. Since all the cells are pith cells, they should have all stained the same colour, but due to incomplete saturation with the dye, it ended up producing a lovely gradient of colours ranging from blue-green to purple-pink.