Sirolimus is a macrocyclic lactone studied for its ability to inhibit the mechanistic Target of Rapamycin (mTOR) pathway. This pathway integrates nutrient and energy signals to regulate cell growth and autophagy. Researchers use sirolimus as a tool to explore mTOR signaling in vitro, investigating its effects on cell proliferation, immune function, and longevity mechanisms. This overview provides an introduction to mTOR research and highlights how sirolimus helps illuminate these pathways. This article is intended for educational and research discussion purposes only and does not provide medical advice or usage guidelines.