Background: Medical advances have improved survival rates for many cancers and other illnesses. This means that more people are coping with the long-term effects of these treatments. Some treatments can cause female infertility. Ovarian tissue cryopreservation (OTC) may help. Before undergoing a treatment that may damage their fertility, patients may opt to freeze a sample of ovarian tissue. The tissue contains immature egg cells. When thawed, the tissue can be reimplanted. This procedure can help women become pregnant. Objective: This natural history study will create a databank of ovarian tissue. The NIH will provide OTC as a clinical service. The NIH will also request a portion of the tissue to use for research. Eligibility: Females aged 4 to 35 who opt to have OTC before receiving cancer treatment. Design: Participants will be screened. Their existing medical records will be reviewed. They will be asked if they want to donate a portion of their ovarian tissue for research. No more than 20% of the tissue collected will be taken for research. Some other tissues that would otherwise be discarded will also be kept. Medical data from each participant may also be collected and stored in the database. This data may include results of routine blood tests, imaging tests, and other information. The data will be coded for privacy. Participants will answer a questionnaire. They will be asked about their fertility treatment and general health. The survey takes about 30 minutes. They will repeat the questionnaire once a year for 30 years.