The last decade has witnessed significant advance in the imaging of living
systems using fluorescent markers. This progress has been primarily associated
with the discovery of different spectral variants of fluorescent proteins.
However, the fluorescent protein technology has its own limitations and, in
some cases, the use of low-molecular-weight fluorophores is preferable. In this
review, we describe the arsenal of synthetic fluorescent tools that are
currently in researchers’ hands and span virtually the entire spectrum,
from the UV to visible and, further, to the near-infrared region. An overview
of recent advances in site-directed introduction of synthetic fluorophores into
target cellular objects is provided. Application of these fluorescent probes to
the solution of a wide range of biological problems, in particular, to the
determination of local ion concentrations and pH in living systems, is
discussed.