The two structures illustrated below are used to demonstrate the extreme similarities between: 

A. Chlorophyll in plants  &  B. "Heme" of Hemoglobin in human blood.

Notice how strikingly similar these molecules are. The structure is centered around a single metallic atom Connected to at least 8 rings, via  4 Nitrogen (N) bonds.  The relationship is even more interesting when we see that they have opposite functions in the respiration of plants and animals.  Hemoglobin, in humans, (when dark red/bluish color)  is bonded to the waste product of respiration of the cells, Carbon Dioxide ( CO2 ). In the Lungs, in the presence of oxygen it will give up the Carbon Dioxide to be exhaled and absorb Oxygen ( O2 ) (turning bright red ) like a sponge.   In contrast, in the presence of light, the chlorophyll in plants will use Carbon Dioxide as a raw material to liberate Oxygen from it. In addition, that energy will be stored in the fruit of the plant as food. If there is no sunlight, or Carbon Dioxide, this will not take place. So the essential oxygen we breathe and food we eat, is a result of the miraculous processes in plants called photosynthesis, because of green chlorophyll.  

green plants are essential to life on earth, and our most valuable food.  the more chlorophyll, the better,  this is the key to vibrant health and vitality !

A.- Chlorophyll with 1 central metallic atom of Magnesium ( Mg - 2+ charge )

B.- Hemoglobin ("HEME" part) with 1 central metallic atom of IRON ( fe - 2+ charge )