this. this is a great big step. they call it the holy grail for all of the reasons that you described. what are the obvious challenges ahead. well there is so many things. every time you solve a problem, new ones open up. so again practical application is probably for our grandkids. but there are so much other br break-throughs that will launch us into an age that is just beginning. i ll take it. i m here for it. they ve been working on if since the 50s. we ll take nerdy wins. any day of the week. thank you. so public health officials in new york city, los angeles, and seattle they re urging people to start wearing masks once again indoors amid the surge of covid, flu and rsv cases we re seeing all over the country and this is happening just as everyone is preparing to zba gather with family and friends for the holidays. l elizabeth cohen joining me now. what is the new guidance. the new guidance for those