Why X- rays are needed to probe the crystal structure ?

Explanation

According to the principles of optics , the wavelength of light used to observe an object must to be no greater than the twice the length of the object it self . It is impossible to see atoms using even the finest optical microscope . To see the atoms we must use light with a wavelength of approximately `10^(-10) `m . X - rays are present with in this region of electromagnetic spectrum .
So X-rays are used to probe crystal structure .