"Hillstreams" is a bilingual educational field guide exploring hillstreams found in Hong Kong. The main emphasis of this book is identification, with some 100 of the commonest species identified for the habitat. Other chapters cover the ecology of the habitat in question, how to get to example sites and what to do once you get there. The series has a number of colour-coded quick-reference systems to help you find a particular organism in the book and identify it, from coloured borders to a simple key, as well as an 'at-a-glance' icon set that provides details on abundance, diet and size, plus other details.