Plants looks at how plants produce blue. From the mystery of why plants are green, the author then shows the challenges of producing blue flowers in plants. People in the past (and chemistry researchers today) have looked at pigments produced by plants to colour clothes and food. While red and yellow pigments are common, pigments for blue are rare and highly sought after. Producing a blue rose is also a target that is yet to succeed (although blue chrysanthemums have been produced). In the past, indigo was a popular blue dye, but now artificial dyes are common.