For several years, micro units — efficiency studios as small as 250 square feet — have been touted as a solution for the region’s housing crisis, allowing developers to wring more units from ever dwindling supplies of land. But the concept has been absent in the South Bay’s market-rate apartment pipeline, despite thousands of units developed during the recovery. Instead, micro units have remained something that happens up in San Francisco, like $4 toast and artisanal pickle b