Chemically, chlorophylls are porphyrin derivatives with a distinct head and tail region. They are insoluble in water but soluble in organic solvents. Chemically, carotenoids (carotenes and xanthophylls) are lipid compounds which are derivatives of lycopene pigment. They too are insoluble in water but soluble in organic solvents. Chemically, phycobilins are also porphyrins derivatives with open tetrapyrrolic chains (no ring, no Mg, and no phytol chain). They are soluble in water.