Take gelatin in a bowl, cover with ¼ cup of water. Let them soak for 10 mins. Take them in a sauce pan. Now heat them on a low heat till it is melted completely.
Take mangoes and peel them. Cube them and take it in a blender and puree till smooth.
Take sugar, 1 cup water in a sauce pan and heat till the sugar is melted.
Now add in the gelatin, mango puree and lemon juice. Mix well.
Pour this into individual moulds and set them in fridge for 3 to 5 hours.