Photosynthetic organisms fuel their metabolism with light energy
and have developed for this purpose an efficient apparatus for
harvesting sunlight. The atomic structure of the apparatus, as it
evolved in purple bacteria, has been constructed through a combination
of x-ray crystallography, electron microscopy, and modeling. The
detailed structure and overall architecture reveals a hierarchical
aggregate of pigments that utilizes, as shown through femtosecond
spectroscopy and quantum physics, elegant and efficient mechanisms for
primary light absorption and transfer of electronic excitation toward
the photosynthetic reaction center.