Mammals are an incredibly diverse and highly successful group of animals. They include some of the tallest, heaviest and fastest animals around today, as well as our own species. For over 100 years, biologists have attempted to build mammal evolutionary trees using anatomical data. This work has provided the basis for our understanding of mammal relationships. Within the last 30 years, new technologies have enabled scientists to cheaply sequence molecular data (e.g. DNA and amino acid sequences) from thousands of mammal species. Interestingly, molecular trees reveal close relationships between some very different looking mammals. To guide us through this mammal renaissance, we are joined by Dr Robert Asher from the Department of Zoology at the University of Cambridge, UK.