Tag clouds have gained popularity over the internet to provide a quick overview of the content of a website or a text. We introduce a new visualisation which displays more information: the tree cloud. Like a word cloud, it shows the most frequent words of the text, where the size reflects the frequency, but the words are arranged on a tree to reflect their semantic proximity according to the text. Such tree clouds help identify the main topics of a document, and even be used for text analysis. We also provide methods to evaluate the quality of the obtained tree cloud, and some key steps of its construction. Our algorithms are implemented in the free software TreeCloud available at http://www.treecloud.org