Some chemical reactions are sensitive to external magnetic field. Majority of them are based on the radical-pair mechanism. Especially, when the radical pair system is in equilibrium with emissive exciplex, the amount of the emission can be modulated with the external magnetic field. In this talk, I will discuss magnetic field-sensitive fluorophores that are composed of chain-linked polyaromatic electron acceptor and amine electron donor, for an example, pyrene-(CH₂)₁₂-O-(CH₂)₂-N,N-dimethylaniline. I will demonstrate several fluorescence imaging techniques that were obtained with the fluorophores and introduce a fluorophore for practical applications of mapping the magnetic field. Under a 375-nm illumination, an image of magnetic field distribution is obtained with it. Its feasibility for obtaining a magnetic field image with two-photon fluorescence microscopy is demonstrated.