If more than half of the nucleus is stained blue there is an excess of histones and chromatin decondensation. During spermiogenesis, the nucleus of the sperm is completely reorganized and becomes highly compact after replacement of the histones with more basic proteins (protamines P1 and P2 according to a precise ratio). This causes the nucleus of the sperm to acquire a high chemical and mechanical stability that protects it during its journey through the male and female genital tracts and during its interaction with the oocyte. In addition to clarifying situations of “idiopathic” infertility, functional tests are used to monitor the effectiveness of a medical or surgical therapy more precisely and evaluate the improvement over time.