A method of preparation of a diversified mixture comprising two or more human milk oligosaccharides (HMOs) the method comprising the steps of a) providing at least one compound or a mixture of the compounds selected from the group consisting of: - optionally sialylated and/or fucosylated lactose derivatives of general formula 4 and salts thereof: wherein R 1 independently of each other is fucosyl or H R 4 independently of each other is sialyl or H, provided that the compound of general formula 4 is not lactose, if provided alone; - lacto-N-tetraose: - lacto-N-neotetraose (LNnT): b) adding at least one enzyme comprising a transglycosidase activity to the at least one compound or a mixture of compounds provided according to step a); c) incubating the mixture obtained according to step b); d) wherein: i. where both: only two compounds are provided in step a) of which one is 3'-sialyllactose or a sialylated lactose derivative of general formula 4, and the enzyme comprising a transglycosidase activity added in step b) is an enzyme comprising a trans-sialidase activity, at least steps a) and c) or steps b) and c) are repeated; ii. where only one HMO is made as a result of step c), at least steps a) and c) or steps b) and c) are repeated; e) optionally repeating at least steps a) and c) or steps b) and c) with the mixture obtained according to step c) or d); wherein the at least one enzyme comprising transglycosidase activity is an enzyme comprising a trans-fucosidase, trans-sialidase, trans-lacto-N-biosidase and/or trans-N-acetyllactosaminidase activity. a) providing at least one compound or a mixture of the compounds selected from the group consisting of: - optionally sialylated and/or fucosylated lactose derivatives of general formula 4 and salts thereof: wherein R 1 independently of each other is fucosyl or H R 4 independently of each other is sialyl or H, provided that the compound of general formula 4 is not lactose, if provided alone; - lacto-N-tetraose: - lacto-N-neotetraose (LNnT): - optionally sialylated and/or fucosylated lactose derivatives of general formula 4 and salts thereof: wherein R 1 independently of each other is fucosyl or H R 4 independently of each other is sialyl or H, provided that the compound of general formula 4 is not lactose, if provided alone; R 1 independently of each other is fucosyl or H R 4 independently of each other is sialyl or H, provided that the compound of general formula 4 is not lactose, if provided alone; - lacto-N-tetraose: - lacto-N-neotetraose (LNnT): b) adding at least one enzyme comprising a transglycosidase activity to the at least one compound or a mixture of compounds provided according to step a); c) incubating the mixture obtained according to step b); d) wherein: i. where both: only two compounds are provided in step a) of which one is 3'-sialyllactose or a sialylated lactose derivative of general formula 4, and the enzyme comprising a transglycosidase activity added in step b) is an enzyme comprising a trans-sialidase activity, at least steps a) and c) or steps b) and c) are repeated; ii. where only one HMO is made as a result of step c), at least steps a) and c) or steps b) and c) are repeated; i. where both: only two compounds are provided in step a) of which one is 3'-sialyllactose or a sialylated lactose derivative of general formula 4, and the enzyme comprising a transglycosidase activity added in step b) is an enzyme comprising a trans-sialidase activity, at least steps a) and c) or steps b) and c) are repeated; ii. where only one HMO is made as a result of step c), at least steps a) and c) or steps b) and c) are repeated; e) optionally repeating at least steps a) and c) or steps b) and c) with the mixture obtained according to step c) or d);