In this chapter, I will argue that a tree diagram provides a visual representation of the long-term, linear relationship among languages, which can be red red to as the net of "macro-comparison." A contrasting idea is "micro-comparison," where language data from geographically close areas are compared and reconstructed. In a micro-comparison. a significant part of the data is expected to consist of local innovations and features acquired through contact, which are known to not be well-represented in a tree diagram. Several points will be made. First, whether it is appropriate to use a tree diagram or not depends on the researcher's viewpoint rather than the actual nature of the development of the language. This will be demonstrated by taking Hawaiian and sign languages as examples. Then, the relationship between the linear developmental paths of languages and other aspects are examined. It is claimed that it is a change of methodology in comparing and reconstructing languages and a change in the linguistic data that is being compared that has resulted in linguists conducting micro-comparison. As a result, linguists have become more aware that what can be expressed with a tree diagram is limited. Finally, it is suggested that, even when the focus of the research is micro- comparison, a tree diagram may still be useful, to show the general context of the development of relevant languages as a visual representation.