This pretty trailing Peperomia occurs throughout Peru, Colombia, and Ecuador.  Its maroon leaves with green leaf venation and ruby red stem make it a very attractive species for its diminutive size.  Leaves only reach about 1/3 inch but it will happily ramble all over your terrarium if you allow it.

Available plants are offered as cuttings approximately 10″ long (or two pieces of 5″).  I tried selling these as potted plants for a while but they are challenging to ship due to their delicate and small leaves.  They ship wonderfully as cuttings in sphagnum moss, though!