Well this is interesting: A Rotterdam, Netherlands-based company, Kraaijvanger, masterminded The Hub, a series of 15-square-meter (that's 161 square feet) modular units containing a kitchen, shower, and toilet and designed to convert any building with water and electricity hookups into a livable space.
Each unit, made of laminated blockboard and solid timber, also includes heating, a sound system, and a Wi-Fi connection, and is meant to be "easily dismantled... when a building gets a new function," according to its architect, David Hess. The Hubs are hooked up to plumbing and electricity via in-floor connections.
Clinching the win in a housing association-sponsored competition in the Netherlands called "How will we live in the future?", the hubs can be arranged one or more per structure, and could be used to accommodate members of any number of demographic groups, including students and refugees to European nations.