The true Begonia microsperma has been a rare & hard to get yellow-flowered African species. For years It has been confused in cultivation with the more common, and VERY SIMILAR, Begonia staudtii.
Begonia microsperma is compact enough for larger terrariums, or definitely grown as a stunning accent in a shady humid greenhouse. Stunningly attractive when full grown and blooming.
Note: From what we've seen, for many years most plants dispersed as B. microsperma in the USA have actually been Begonia staudtii and thus creating a lot of confusion. So, if you have a B. "microsperma" (even those from us that you obtained prior to Sept 2016), there's a good chance that you're growing B. staudtii. The discernable differences between these two species are slight - however, "True" B. microsperma has somewhat slimmer / narrower leaf outline with a more distinct drip-point to the leaf tip. The petioles (leaf stems) are comparatively sparsely bristled, while those of B. staudtii's are quite hirsute.
These are husky, established, cutting-grown plants, currently in 2-3" pots.