  Many crystals in nature exhibit fascinating mechanical, optical, magnetic and
other characteristics. One of the reasons for this phenomenon has to do with
the presence of specific organic molecules that are tightly associated with the
mineral. Over the years, some organic crystals have been found to be located
within the lattices of their singlecrystalline biogenic hosts. A number of
questions remain unanswered: for example, how do these molecules become
incorporated and what is their function? In this review we survey the gradual
refinement of the above mentioned finding in biogenic crystals, with the object
of tracing the acquisition of our fundamental knowledge in this field during
the last 50 years. We highlight the progress made in understanding the function
and significance of this intracrystalline organic matter, from the earliest
observations of this phenomenon in a biological system to the highly promising
recent achievements in bio-inspired material synthesis, where intracrystalline
molecules have been used in many studies to synthesize numerous synthetic
nanohybrid composites with fascinating new properties.

Materials Science