A short overview of research into design of molecular opto-electrical switches is presented. Theoretical results obtained on microscopic systems are supplemented with experimental results measured on macroscopic structures fabricated using molecular materials. It is shown that, beside optical switching of the type: "optical input'' - "optical output'', photochemically driven photochromic reaction may be, under certain conditions, used as a controlling step in "optical input - electrical output'' devices. Several possible architectures of such systems are described.