Occupational, disciplinary and institutional identities are formed and reformed over the lifetimes of practitioners and subsequently through devices such as portraits, biographies, entries in reference books and websites. These genres and cultural forms shape the ways individuals understand themselves and their contexts and constitute forms of public culture, thereby providing historians with valuable sources. Such intricate processes may continue over hundreds of years, as we know from the life and afterlives of William Harvey (1578-1657), for example. I shall explore images, tags and identities and reflect on the approaches we can use to probe them, showing how they shed light on themes such as the history of ‘scientific method’, disciplinary labels and the ways in which practitioners use both the past and the present to represent their endeavours to themselves, each other and wider audiences. They did not work alone, but collaborated with artists and writers, collectors and administrators. Historians too are active participants in these processes. Michael Foster (1836-1907), with his interest in the past of his field and his status as the creator of a research school, is a pertinent example. He is described in the Oxford Dictionary of National Biography as ‘physiologist and politician’, an intriguing example of a ‘tag’. To state the point in more general terms, I want to explore categories and categorisation, historians’ own as well as those of historical actors.