This review explores the optical phenomena in molecule-based magnetic materials, highlighting their potential applications in various fields such as sensors, data storage, spintronics, and quantum computation. The authors discuss the development of molecular magnetism, which involves magnetic materials based on organic radicals and metal complexes. They focus on ferro-/ferromagnetic materials, spin transition materials, molecular nanomagnets, and stimuli-responsive magnetic materials. The review covers various optical phenomena, including thermochromism, photoswitching, luminescence, nonlinear optics, and chiroptical effects. These phenomena are explored in the context of different classes of molecule-based magnetic materials, such as magnetically ordered systems, spin transition and electron transfer materials, and molecular nanomagnets. The review also discusses the recent advances in high-temperature photomagnetism, optical thermometry using single-molecule magnets (SMMs), optical addressability of molecular qubits, magneto-chiral dichroism, and opto-magneto-electric multifunctionality. The authors emphasize the importance of linking optical and magnetic properties in these materials to achieve multifunctionality and multi-stimuli responsiveness, which are crucial for advanced devices and applications.This review explores the optical phenomena in molecule-based magnetic materials, highlighting their potential applications in various fields such as sensors, data storage, spintronics, and quantum computation. The authors discuss the development of molecular magnetism, which involves magnetic materials based on organic radicals and metal complexes. They focus on ferro-/ferromagnetic materials, spin transition materials, molecular nanomagnets, and stimuli-responsive magnetic materials. The review covers various optical phenomena, including thermochromism, photoswitching, luminescence, nonlinear optics, and chiroptical effects. These phenomena are explored in the context of different classes of molecule-based magnetic materials, such as magnetically ordered systems, spin transition and electron transfer materials, and molecular nanomagnets. The review also discusses the recent advances in high-temperature photomagnetism, optical thermometry using single-molecule magnets (SMMs), optical addressability of molecular qubits, magneto-chiral dichroism, and opto-magneto-electric multifunctionality. The authors emphasize the importance of linking optical and magnetic properties in these materials to achieve multifunctionality and multi-stimuli responsiveness, which are crucial for advanced devices and applications.