We have seen that tone and segmental duration must be autosegmentalized in order to account for a number of phonological phenomena. In this chapter, we will continue this theme. We will replace the matrix comprising the remaining distinctive features with a hierarchical configuration of these features. We will begin by considering a number of arguments for replacing the unstructured list of laryngeal, manner and place features with a feature tree. The main advantage of this ‘autosegmentalized’ representation is that features or particular groups of features can spread to neighbouring segments, which greatly improves the description of assimilation processes. Moreover, the assumption made in Chapter 6 that not all segments are specified for all features appears to have interesting consequences in the new model. Some of these will be discussed in this chapter, while others will be discussed in Chapter 13, which continues this topic.