'Clearing the smoke': Where cannabis culture and medical research stand on 4/20

April 20 or "420" has long been commemorated as an unofficial holiday for cannabis — but how did it get started? And what place does it hold in popular culture today?Monday on Midday Edition, we look at how April 20 became the cultural phenomenon it is today, the holiday's activist roots, and the current landscape for cannabis at a national, state and local level.Then, it's been 30 years since California became the first state to legalize medical marijuana. We check in on the state of cannabis research today.Guests:Jackie Bryant, journalism professor, San Diego State University, editor, Leaf MagazinesDr. Igor Grant, director, Center for Medicinal Cannabis Research at UC San Diego