Classification of Sex Maturity Stages in Boys Tanner Genitalia Pubic hairs stages 外生殖器 阴毛 PI prepubertal GI PHI None P2 early stage G2 PH2 Scanty, long, slightly pigmented pI P3 metaphase G3 PH3 Darker start to curl small in amount P4 anaphase G4 PH4 Resembles adult type less in quantity, curly P5 adult stage G5 PH5 adult distribution rhombus in shape