This review emphasises the need to use spectroscopy in order to understand
the behaviour of water, and summarises the background of the subject. The v
arious forms of spectroscopy that are especially informative are described,
with particular reference to near-infrared (NIR) spectrophotometry. The ke
y results are outlined, first those obtained with small molecules and ions,
and second those involving proteins, DNA and cell membranes. Finally, some
interpretations are offered which include the novel but possibly controver
sial concept of free OH and free lone-pair groups.