Electromagnetic radiations affect human health seriously. Bio-effects of electromagnetic fields mechanisms closely depend on the properties of themselves. Moreover, electromagnetic properties of signaling molecules, radicals and magnetic particles within body will be changed in electromagnetic fields, especially the conductivity, dielectric and magnetic properties of biological tissues will be significant difference when biological tissues exposure to various frequency electromagnetic fields. Identifying the evolution of electromagnetic properties of biological tissues is a key issue to explore underlying mechanisms and prevent electromagnetic bio-effects. Effects and applications of biological tissues in electromagnetic fields are summarized, and several future research directions are put forward.