Based in Edinburgh, Calleja (b.1981 Malta) holds a Masters degree in the interdisciplinary course, Art Space and Nature from the University of Edinburgh. He is a practicing visual artist and a board member of Lateral Lab, an arts charity based in Fife, Scotland. His work was shortlisted for Saatchi and Channel 4 New Sensations 2010. This culminated into a show in London alongside leading contemporary artists as curated by Wolfe Von Lenkiewicz and Victoria Golembiovskaya under the title House of the Nobleman . He was selected for the New Contemporaries 2011 by the Royal Scottish Academy. He was also the first recipient of the Robert Callender Residency for Young Artists, a residency that took him to Osaka and offered him a solo exhibition in Kyoto.

Alongside his own art practice, Calleja has assisted several artists in the development of their work, in particular he worked closely with environmental artist Elizabeth Ogilvie on her project Out of Ice and continues to collaborate in projects as led by Lateral Lab. In 2016, Calleja has shown his work, untitled alongside Katie Paterson's History of Darkness in the exhibition Mediated Existence, with I Chern Lai, curated by Naoko Mabon with the support of Ingleby Gallery and Collection Simon Paul.