Since fluorescent PET sensors are based on rather small (ca. 1 nm)
molecules, they can enter living cells and remain undetected by the cell
machinery for reasonable periods of time. During their residence, these
molecules act as little James Bonds and gives us a window into the
private lives of protons, for instance \cite{probescom}.
Fluorescent PET sensors switch their emission signal rather sharply upon
encountering the target species, e.g. from ‘off’ to ‘on’. Such switching
of signals is similar to those seen inside computers and we
recognized this connection between disciplines in
1993 \cite{de_Silva_1993}. The field of molecular logic-based computation
arose as a result \cite{de_Silva_1993,Ling2015}. Over 610 laboratories have
joined this field (Figure \ref{816506}). Many logic gate arrays of varying degrees
of small-scale integration have now been constructed. Some of these have
been operated within small spaces, some of which are alive. Since these
small spaces are not usually accessible by semiconductor logic devices,
they are virgin territory for exploration by intelligent molecular
devices \cite{Ling2015}. Even certain aspects of human behaviour can
be emulated by molecular logic-based computation
already . More progress along these lines can be
expected \cite{Ling2015a,Ling2015b,Ling2015c}.