Bella finds out all about some of the smallest mammals in the UK - mice! Chantelle visits a wildlife group to meet Sean, Mossy, Gabriela and Cara and help them release harvest mice into the wild. Rory and his son Sandy are at a farm looking for mice.

Chantelle and Rory's fact files explain about prehensile tails, where mice find food, how many babies they have and whether or not they hibernate. It's also time to find out what mice do to help the planet! This episode's Teeny Tiny Task is to make a tennis ball house for harvest mice.

Amiah-Rae finds out all about some of the smallest underwater creatures – seahorses! Chantelle meets seahorse fans Joss and Gabriel and puts on her wetsuit for an underwater safari. Rory and his son Sandy are at an aquarium just in time for seahorse feeding time.

Chantelle and Rory's fact files explain how seahorses hide, how they use their prehensile tails and how many babies they have. It's also time to find out how seahorses help the ocean – in the food web and as an indicator species. This episode's Teeny Tiny Task is to make some seahorse art with recycled beach materials.