The possibility of controlling and manipulating the electronic properties of a material by an external stimulus is an attractive challenge in material science. In this context, photomagnetic materials showing light-induced modifications of their magnetic and optical properties are the object of study for both fundamental aspects and potential applications. In this presentation, we will show how several physical stimuli, light irradiation but also temperature or pressure changes, can induce reversible metal-metal electron transfer in Fe-CN-Co bridging units, leading to drastic changes in optical or magnetic properties. We will also illustrate with some of our recent studies[1] some of the challenges we face in order to better understand and improve the switching of the physical properties.