‘They are formed from chaos, from the random swirling of water vapour that condenses molecule by molecule, with no template to guide them. Whence this branchingness? Wherefore this sixness?’ This is Philip Ball, in his grand and mildly pompous style, describing how a snowflake forms. Branches (like this review) starts with concrete details rather than a general introduction. And the book (but not this review) starts as it means to go on: it has lots of examples and plenty of themes, but no thesis. But don’t let it put you off this rich, thoroughly-researched exploration of trees, rivers, bacteria, cracks, cities, and other kinds of branching growth. The reason Branches lacks an introduction is probably that it is one third of a trilogy that Ball published as one volume back in 1999, and Branches has not quite disentangled itself from the other two books (see also Shapes and Flow ). Ball often ‘reminds’ the reader of what they ‘learned’ in Book I or Book II. And the conclusion ...