The synapsis process occurs in the prophase I stage of meiosis. In synapsis, replicated homologous chromosomes link, which become known as a tetrad. Crossover between two pairs of tetrads can occur at any time.
During synapsis, the homologous chromosomes start with their ends attached to the nuclear envelope. The chromosomes then migrate until the matching ends have been paired together. The piece that connects the chromosomes after the paring is called the synaptonemal complex, which is a protein structure. This stage is often confused with the prophase that occurs in mitosis, but they perform different functions and do not produce the same results.