Tiny plants for tiny terrariums are mostly sold as groundcovers. Look for the dark green \"Baby Tears\" or mint smelling \"Corsican Mint\" or even miniature African Violets and tiny bog plants. The fact that your containers are sealed with a cork stopper means that sedums and succulents will not work because the humidity that will be trapped inside the glass is going to rot any plant that needs good drainage. The place to find these tiny plants is the houseplant section of an independent nursery that has terrarium supplies. Perhaps the easiest terrarium to make with a cork top is to layer in gravel, soil and moss from a tree trunk or stone. Then add a tiny focal point accent, something you cannot kill like a tiny bench or figurine. The moss will stay low but thrive in the high humidity. Other plants, even dwarfs will grow too large for the small space in just a few months. Good Luck and Keep growing, Marianne Binetti