"But I am not afraid to consider the final question as to whether, ultimately -in the great future- we can arrange the atoms the way we want; the very atoms, all the way down!"

R. P. Feynman1

GFP and GFP-like proteins allow the monitoring in time and space of an ever-increasing number of phenomena in living cells and organisms, like gene expression, protein localization and dynamics, protein-protein interactions, cell division, chromosome replication and organization, intracellular transport pathways, organelle inheritance and biogenesis, to name but a few2. In addition, the fluorescence from single GFP molecules has made it feasible to image at a spatial resolution higher than the diffraction limit. Furthermore, sensors that report pH values, Ca2+ concentrations and other essential features of the interior of living cells have been engineered from GFP-like proteins2.

In this site, we present an overview of scientific applications of GFP from Aequorea victoria and GFP-derived fluorescent proteins; then, we focuse on a subset of these applications, i.e. the so-called reporters or biosensors of biochemical activities.