This review highlights the effectiveness and robust nature of eco-friendly room-temperature polymerization initiated in emulsions, and some of its applications in polymer and materials science. The polymerization in emulsions initiated through a thermal or redox approach can be safely conducted under ambient conditions without using other hazardous chemicals. Thermal initiators decompose efficiently at the surfactant-stabilized oil-water interfaces at room temperature. The interface-induced initiation is found to be somewhat independent of surfactant type, insensitive to oxygen, and works for several thermal initiators. Redox initiators without transition metal compounds also effectively initiate room-temperature polymerization in emulsions. With the assistance of room temperature initiation, the polymers synthesized at room temperature are of high molecular mass. In addition, room-temperature polymerization allows temperature-sensitive molecules, for example, proteins and enzymes, to be incorporated with the polymers in situ. The applications of room-temperature polymerization in high internal phase emulsions and biomedicine are also discussed. The initiation of radicals from oil-water interfaces or transition metal-free redox systems is a promising eco-friendly method to promote radical reactions at room temperature.