Organizers of a special purpose acquisition companies ask investors to give them money to form a publicly listed shell company. These sponsors, who typically invest a modest sum while awarding themselves 20% of the shell, then hunt down a privately held target company that would like to go public. It's an opportunity for investors to get potentially high returns in an era of ultra-low interest rates. And for the target companies, especially those who might otherwise have struggled to go public, it's a speedy route to an IPO. Virgin Galactic, Draft Kings, and, more recently, the genetics firm 23andMe and the dog-walking app Rover, have all agreed to be purchased by a SPAC.