This is nine-year-old Carter, a periodicvideos fan from the US.
Carter's Mum told us:
"He has even asked for ferrofluid for his birthday and cesium for Christmas!
"Thank you for such wonderful videos!
"We love to watch your educational videos at bedtime to help 'wind down' after long days.
"Thank you for all of your had work!! You guys are fun and informative and we can't get enough!!!
"We watch and re-watch your wonderful videos almost daily!"
MORE FAN PHOTOS