Tansy (Tanacetum sp.) leaf. Coloured scanning electron micrograph (SEM) of the surface of a leaf from a tansy plant, showing the hairs (trichomes, spiky) that cover its surface, along with the glandular hairs (yellow), in which the essential oils are stored, which give the leaves their strong aroma. Also seen are stomata (dark, round), which are microscopic pores through which gas exchange takes place. Magnification: x200, when printed 15cm wide.