	Every regular matroid, and every graphic matroid, is binary. A binary matroid is regular if and only if it does not contain the Fano plane (a seven-element non-regular binary matroid) or its dual as a minor. A binary matroid is graphic if and only if its minors do not include the dual of the graphic matroid of formula_20 nor of formula_21. If every circuit of a binary matroid has odd cardinality, then its circuits must all be disjoint from each other; in this case, it may be represented as the graphic matroid of a cactus graph.