The most common standard for adult collectors is 1:12 scale, also called 1" or one inch scale (where 1 foot is represented by 1 inch.) Among adult collectors there are also smaller scales which are much more common in the United States than in Britain. 1:24 or half inch scale (1 foot is 1/2") was popular in Marx dollhouses in the 1950s but only became widely available in collectible houses after 2002, about the same time that even smaller scales became more popular, like 1:48 or quarter inch scale (1 foot is 1/4") and 1:144 or "dollhouse for a dollhouse" scale. 1/24th scale dolls houses, and those in smaller scales, may be considered as just one species of miniature houses of this size. 1/24th (or the almost indistinguishable 1/25th) is used for a variety of models including display models and what are coming to be known as 'house portraits'. These typically focus on the exterior detail rather than the rooms inside, though there is no reason why a dolls house should not have a realistic exterior or a house portrait include interior details.