The educational material of this manual is addressed to students and teachers of primary and secondary education, in particular, to students in the last three grades of Primary School and High School students. The goals are for the students to get interested in correct basic knowledge about “Energy” in general, to understand how to rationally use it and save it in daily life, the effects on the environment and the climate of planet Earth from its (ab)use, and to participate in actions to deal with them. The basic aim is for the material to be presented in a simple and comprehensible way, to be interesting and exciting for students, so as to arouse their interest, create concerns, motivate them to take action and change their behaviour. At the end of each chapter, there are activities for students, that can be done either at school or at home with the cooperation of their parents.