Idiomatic expressions reflect the thought processes and ways of life of a people. Although the teaching-learning process of such expressions leaves more than one perplexed, many are concerned that the usage of these expressions confirms the authenticity of one's verbal exchanges. Consequently, it is worthwhile to make them one's own. An expression can, in turn, take on a certain meaning in one language but not in another. Which expressions should be recommended and why? How does one go about teaching them? At what level of linguistic competence in one's second language should these expressions take on importance and starting at what age? Using previous studies on this subject as reference, we shed light on how to teach and learn idiomatic expressions in a second language; it is here that knowledge and expertise come together. By making connections between theory and practice, we show how the pleasure of learning a second language can develop, among other things, through idiomatic expressions.