Studio 37 a 400 sq ft Modern Pre-Fab From Small Modern Living. Although not strictly tiny house builders, they certainly have the talent for it.
From the designer:
Designed to be a very simple and versatile 400ft2 unit, studio37 can be adapted to meet most design requirements and work in most yards. Careful attention to details allows this unit to maximize space with an efficient interior layout.
Enjoy the photos and the floor plan layout at the bottom.
More Info at Small Modern Living