The purpose of this agreement is to have CDC conduct environmental exposure assessments as part of the BCERP epidemiology project to facilitate common goals in understanding the biological basis of the effects of environmental factors on the age of the onset and progression through puberty of a diverse population of pre-and peri-pubertal girls in the United States. The BCERP sites will collect and forward biospecimens to CDC laboratory and CDC will do all necessary sample preparation, analysis, coding, reporting and return of leftover spamples to the Investigators or for disposal.