ree that is both balanced and has a full set of leaves. A MMR is a list of perfect binary trees, called <i>mountains</i>, each of strictly decreasing height. The leaves of the MMR store the (positioned) hash of each element in the order of their insertion. We won't cover all the details here, but note that this structure is easy to maintain: if you add a new element to the end of the list, you need only generate at most a <i>log2(N)</i> number of new internal nodes to re-impose the required properties witho