Plants are pretty amazing things when you think about it, which most of us probably don't an awful lot.
We take our plants for granted, never thanking them for all the wonderful oxygen they produce, without which complex life (like us) would be impossible, or at least very different from the way it is now.
Plants form one of the four great 'kingdoms' of life, the others being animals, fungi and bacteria (plus the archaebacteria).
Life began on Earth around three and a half billion years ago, and for the next two and a half billion years consisted of nothing but bacteria and their close relatives the archaebacteria.
Then, a little over a billion years or so ago, something extraordinary happened.
Two single-celled organisms somehow became fused and learnt to work together.
Actually, we know this must have happened at least twice, as two distinct structures exist in plant and animal cells to this day - mitochondria in plants and animals, and chloroplasts in plants - that lead quite independent lives in our cells.
These two structures, or 'organelles', are responsible for absolutely critical functions, and complex life could not exist without them.
Mitochondria convert the food we eat into the energy we use, and chloroplasts are where photosynthesis takes place.
In other words, if we imagine that plants are chemical factories, constructing their leaves, stems roots and flowers using the energy of the sun, then chloroplasts are where the actual chemistry takes place.
Here the plant uses energy from the sun to power the production of sugars, proteins and other building blocks of life.
So the very first plant would have been a very simple alga.
Over hundreds of millions of years, these simple plants and their progeny have evolved into every species of plant we can see around us, from the tiniest alga, almost unchanged in over a billion years, to huge Redwood trees, and every little flower and shrub in between.
In all, we know of about four hundred thousand different species of plant, and the total number of species is estimated to be over a million.
Each and every one of these plants and their ancestors has managed to survive, and in many cases plants avoid being eaten by producing bitter-tasting or poisonous compounds.
Other plants have evolved scented flowers to attract different kinds of insects to pollinate their flowers, others have evolved chemicals to make their roots inedible.
What this all means is that an almost unimaginable number of different chemicals have been synthesised by plants.
Some of these chemicals are poisonous to us, some taste good (and some really bad) and some of them have medicinal applications - we can use them to treat or prevent illnesses, or to aid recovery.
Now that we are in a position to understand plant chemistry completely, and to test how different plant chemicals can be used medicinally, plants are becoming more rather than less important to our health and wellbeing.
All over the world, the race is on to isolate plant compounds that can be used in the fight against cancers, HIV and all manner of currently incurable conditions.
We may by chance stumble upon a compound of the right shape and composition to treat a particular illness by randomly synthesising compounds in the lab, but we may find that Mother Nature has already produced the perfect compound, thanks to the quiet and constant evolution of plants over hundreds of millions of years.