Enhancement is a collection of short stories that consider what life would be like if humans drew energy directly from sunlight. Why have we not altered our bodies so we can photosynthesise?
How much of life would change if we could do so? Perhaps we would eat less, rest more, reduce our damage to the environment, maybe live far into our hundreds.
 
An Australian university student starts the world down this path by extracting algae from corals and implanting it into human skin cells.
 
After his success, the technology spreads around the globe until the number of people able to photosynthesise reaches the hundreds of millions, but the proliferation stalls when nations push back, claiming the enhancement is bringing about the end of humanity.