The comprehension, retention and production of idiomatic expressions is one of the most difficult areas of the lexicon for second language (L2) learners, even very advanced students, to master. This book investigates this under-researched and interesting aspect of language acquisition, shedding light on both conventional uses of idiomatic expressions as well as creative variant forms. The chapters in the book delve into different aspects of idiomatic mastery: students' comprehension of canonically used idioms in both their first and second language; the effects of multimedia and visualization techniques on learners' comprehension and retention of L2 idioms; students' misinterpretations of L2 idioms; L2 learners' comprehension of creative idiom variants and their use of idioms in free composition writing.