When Krishna and Balarama were playing, the symbol of Lord Vishnu stuffed a modest bunch of mud into his mouth. At the point when Krishna's companions grumbled to his mom. Yashoda rushed to him and requested that he open his mouth. At first, he declined to. However, when Yashoda gave him a harsh look, Krishna obliged. 

What Yashoda saw wasn't mud however the whole universe. That is the point at which she understood that Krishna was the Lord in mask!