Chemical biology approach enables us to understand the complex biological systems using small molecules such as specific activator or inhibitor of protein, hormone-like inducer and neurotransmitter, etc. To clear the relationships among chemicals and the effect of ascidian development, we reviewed past articles have described the use of small chemicals in the field of ascidian biology. The Ascidians Chemical Biological Database (ACBD) is a database for studying both chemicals and ascidians.