Chlorophyll: the green stuff

Chlorophyll is the stuff that makes plants look green. The chlorophyll molecule is shaped like a tennis racket (the tail in the drawing is bendy because I ran out of space). In the middle of the big flat bit is a single magnesium atom. This is why magnesium is an important nutrient for plants; no magnesium = no chlorophyll = no photosynthesis = no energy .

The tennis racket head bit of chlorophyll is similar to parts if the haemoglobin molecule that is found inside your red blood cells.