New techniques to prepare iodinated derivatives are presented which involve vapor diffusion of iodine and hydrogen peroxide. One of the techniques, termed as Vaporizing Iodine Labeling (VIL) only requires a small amount of KI/I₂ droplet to be enclosed into a crystallization well, where iodination of tyrosine residues in target proteins are sometimes occurred. When the iodination is insufficient for phase calculation, a following technique using hydrogen peroxide (HYPER-VIL) further catalyzes the iodination reaction. These techniques are especially useful for phase determination using longer-wavelength X-rays.