Thermoactive materials changed minds in smart materials research some years ago, resulting in a generation of new high-performance materials and an increased focus on controlling structure, flexibility and smart output, as well as implementation into device applications. Particularly, thermoelectric (TE) and thermomagnetic (TM) materials have been attracting increasing interest, being TEs capable of directly converting temperature variations into electricity and, analogously, TMs materials able to convert temperature variations into magnetic fields. Due to those smart properties, those materials are highly used in thermoactive generators and thermoactive sensor devices, among others. This work reports on the structure, properties and uses of thermoactive materials as well as the main materials optimized for the development of applications. Additionally, recent advances in the design and properties of thermoelectric materials, modelling approaches and some relevant applications are presented.