Length functions as an important element of lexical contrast, opposing singletons and geminates in various unrelated languages all over the world. A growing body of research has been conducted on the phonetics and phonology of this contrast over the last few decades. This chapter offers a general overview into this research, focusing on gemination in Tashlhiyt. It provides a concise summary of previous and ongoing research, including the nature of the phonological representation of gemination, and how the articulatory and acoustic-perceptual characteristics of geminates account for their phonetic pattern. Tashlhiyt is an excellent case in point since, most unusually, it has contrastive geminates initially and finally as well as medially, and presents different types of geminates, including lexical, morphological and phonological geminates.