Condoms and microbicides are methods to prevent the transmission of sexually transmitted infections like HIV. Condoms have been used for hundreds of years and come in different types like latex, lambskin, and spermicidal varieties. When used consistently, condoms can reduce the risk of HIV transmission by 80-97%. Microbicides are substances applied vaginally or rectally to reduce STI transmission and are being developed as gels, films, and rings. They offer benefits like female control and protection without a partner's knowledge. Challenges in developing effective microbicides include a lack of surrogate endpoints for efficacy and ensuring large clinical trials can demonstrate their incremental effects over condoms.