This book focuses on the need of training teachers to apply CLIL methodology to the current education system. There is already research written on the need of applying CLIL methodology to the present education system in order to satisfy the needs of the global society in which the command and the appropriate use of languages is becoming essential in the world today. In fact, there have already been some initiatives at different centers in Spain to apply this methodology. However, after considering these previous experiences, I believe in the imperative need of training teachers to apply successfully CLIL methodology. Therefore, this book presents an experiment in which students of English philology at Universitat Jaume I elaborated a didactic unit for a subject in secondary education to be implemented following CLIL methodology. These didactic units were analyzed empirically and the results showed information and data that could identify some student’s characteristics and needs, which in further research may determine the way to prepare a training plan for future teachers to implement CLIL methodology efficiently in secondary education.