Prophase I is the longest phase of meiosis and is further sub divided into 5 phases :

Leptotene : Condensation makes chromosomes become distinct and compact.

Zygotene : Homologous chromosome start pairing together by a process called synapsis to form a complex structure called synaptonemal complex. Two synapsed homologous chromosomes form a complex called bivalent or tetrad.

Pachytene : Longest phase of prophase I

Recombination nodules appear in this stage at the sites where crossing over has to take place between non-sister chromatids of homologous chromosomes.

Diplotene : Synaptonemal complex dissolves and recombinants separate from each other except at crossover sites to form X-shaped structure called chiasmata.

Diakinesis : Chiasmata terminalises and chromosomes condense. Meiotic spindle assembles and nucleolus and nuclear envelope disappear.