Micro Units are allowed in Boston.

2010

Boston zoning code is amended to allow what are also called “innovation units” in new residential developments. They can be less than 450 square feet, but are only allowed in the so-called “Innovation District” in the Fort Point Channel area. The amendment is expanded to allow so-called “metro units” as small as 450 square feet in areas that are within one mile of public transportation.

Sources
  • Boston Globe