Truffles are underground and extremely expensive mushrooms. They are sometimes sold at charity auctions at extremely inflated prices. They are divided into three groups – black, red and white. The white truffle is the rarest and therefore the most prized truffle. It grows mainly in Italy, France and Croatia, but it is also found in Bulgaria. Specially trained dogs are used to find it. The white winter truffle is considered one of the greatest delicacies in the world. It is mainly traded in Italy, France, USA and Germany. Truffles are also classified by size, with larger ones being more valuable. They are also graded depending on the size, injuries or worming.