Small to very small beetles (1-3mm), there are 56 species in Britain.  Generally brown to reddish-brown, they have a rather characteristic appearance, with an angular pronotum and a rather fat-bottomed appearance as the striate elytra bulge out towards the apices.  They are found in a diverse range of habitats including compost heaps and leaf litter, fungoid bark, rotting fungi, mature Myxomycetes, and indoors in mouldy areas of plaster, wallpaper, wood, etc.  Dissection is required to reliably identify many species.