Since the discovery of the psbF twintron, several categories of twintrons have been characterized. A twintron can be simple (external intron interrupted by 1 internal intron), or complex (external intron interrupted by multiple internal introns).
Following the identification of the psbF twintron, several categories of twintrons have been characterized. A twintron might be straightforward (an external intron with a single internal intron) or intricate (an external intron with multiple internal introns).