Microhouse "Smart Module" and other designs.

Microhouse is a Seattle based design firm, that according to their website, includes architects, landscape architects, and designers.  They specialize, as their name suggests, in small house designs.  They promote these designs as backyard cottages or ADU's (accessory dwelling units), and they range in size from 120  up to 1,200 square feet. 

Smart Module axonometric drawing

Prefab "Dwelle.ings" by Dwelle.

Dwelle. is a U.K. based building design company.  They have a full line of tiny prefab buildings that include two tiny homes (about 250 and 150 square feet respectively), plus a tiny office structure and an even tinier "beach hut."  They even have a stand-alone backyard gym complete with sauna and hot tub.  I have chosen to focus on the two tiny home models.