TODAY | July 22, 2013
>>> back now at 8:49 with a milestone for a man who inspired and educated millions of you minds. bill nye the science guy .
>> here's mara -- how do you say her last name? i always get that wrong.
>> reporter: nothing in your world would be here without science .
>> he is part teacher, part crusader.
>> climate change is happening.
>> part mad scientist .
>> static electrical charge.
>> reporter: known to a generation of americans as the science guy. bill nye spent his entire professional life with one lofty goal in mind.
>> dare i say it? change the world .
>> reporter: and change the world he has. this fall marks the 20th anniversary of his award winning children's tv show bill nye the science guy . the show ran for 5 years, won 18 emmy awards and introduced kids to subjects like magnetism, electricity.
>> it's building up in my rocker wig of science .
>> reporter: and energy.
>> a lot of it comes from the heat released by burning coal.
>> the idea of the show was to get kids into science . i took my heart and soul into it. it took a lot out of me but it was worth it.
>> reporter: it was filmed in a warehouse in seattle with the blue lab coat and signature bow tie .
>> here are the bow ties . they don't wear up.
>> reporter: a fashion trend that began for him way back in high school but don't let his friendly appearance fool you.
>> the warm is getting warmer. it's continually getting warmer.
>> reporter: bill nye has become a fire brand for science , an advocate regularly speaking out about topics like evolution and science change.
>> that's science . that's facts. you can't close your eyes and make them not true.
>> we still have this culture or this tradition where people don't accept science . and that is not in anybody's best interest.
>> reporter: this video he did for the website the big think.com went viral viewed more than 5 million times.
>> i say to the grown ups , if you want to deny evolution, that's fine. but don't make your kids do it because we need them.
>> reporter: today, the same kids that grew up watching bill on tv fill up college auditoriums around the country just to hear him speak.
>> i want you to change the world in new, exciting, and big ways.
>> reporter: their reactions alone priceless.
>> we love bill nye .
>> reporter: proof he's gone from tv icon to scientific rock star .
>> keep reaching, keep seeking.
>> i don't think i get it. the impact of the show. these students say you're the reason i'm in engineering. you're the reason i became a physician.
>> i can't remember a time in my life where i didn't watch bill nye the science guy .
>> reporter: they were inspired by bill. part of the next generation of science educators, their popular website makes the subject entertaining for kids of all ages. much like nye did 20 years ago.
>> these people that used to watch the show, they're going to be the future. it's really gratifying. like that was the idea, wow it came true. but it took a couple of decades.
>> reporter: for today, nbc news new york.
>> we love him.
>> it just reminds you why a great teacher is everything.
>> you know, to make science and math exciting for kids. that's great.
>> he is shooting a documentary called objective change the world . i think he may have