Dear student.
Fat soluble vitamin such as A, D, and the exception (B12) are stored in our body in liver and fat tissue(adipose).
Vitamin B and C are generally not stored in our body and is expelled out through urine when there is excess. It is replaced through the diets.
Vitamin D, A, K, B3 are inherently produced from skin, beta carotene, gut flora and Tryptophan respectively.
Regards.