microSD and miniSD are smaller variants of the SD (Secure Digital) flash-memory based storage cards. While miniSD is small (0.84 inches x 0.78 in. x 0.05 in.), microSD is even smaller at 0.43 in. x 0.59 in. x 0.039 in.
"MicroSD vs MiniSD." Diffen.com. Diffen LLC, n.d. Web. 28 Nov 2014. < http://www.diffen.com/difference/MicroSD_vs_MiniSD >