A structure which is made up of both foetus and maternal tissue is known as:

Explanation

The placenta is an organ that develops during pregnancy and is composed of both fetal and maternal tissue. It forms within the uterus and serves as a site of exchange between the maternal and fetal circulatory systems, facilitating the transfer of nutrients, gases, and waste products between the mother and the developing fetus. Maternal blood flows through the placenta, while fetal blood flows through the umbilical cord, allowing for the exchange of substances without direct mixing of the bloodstreams. The placenta also produces hormones that are important for maintaining pregnancy and supporting fetal development.