PESSTO objects (filled blue stars) in the phase space of cosmic transients as originally developed by Kulkarni et al. (2007). The grey areas illustrate the known phase space for novae, luminous blue variable eruptions and core-collapse supernovae (the common types II and Ibc). The black squares show eruptive transients lying outside the nova regime, and the black dots are supernovae (normal and superluminous) or extreme erupitve events such as SN 2008S (taken from Kulkarni & Kasliwal 2009) The colour for each event represents the colour at peak brightness (B − V or g − r< 0.2 in blue; B − V or g − r> 0.7 in red).