Physical spin crossover (spin transition), one of the most fascinating dynamic electronic structure phenomena occurring in coordination compounds of third row transition metal ions, mostly of iron(II), iron(III) and cobalt(II), has attracted increasing attention by many research groups. Some examples for physical and chemical induced spin crossover are discussed. Among the physical is the temperature and pressure induced switching. Novel effects observed by irradiation and magnetic and electric field will be discussed. Some chemical induced switching effects caused by solvation, ligand exchange, ligand isomerisation and bond breaking will be briefly outlined.