How ccp structure have 4 spheres

Face centred  cubic  (fcc)   or   Cubic closed pack (ccp) -  these are the two names for the same lattice.

We can thhink of this cell as being made by another atom into each face of a simple cubic lattice -  hence the " face centred cubic "  name .

In such a unit cell there are atoms at all the corners , and at the centre of all the faces of the cube.

Each atom located at the face - centre is shared between two adjacent cells and only half of the atom belongs to a unit cell. Thus ,the number of atoms  in this cell  are ,

(i)    8 corner atoms  x  {tex}\frac{1}{8}{/tex} atom per unit cell   =   8  x  {tex}\frac{1}{8}{/tex} =  1 atom

(ii)   6 atoms  at the faces x{tex}\frac{1}{2}{/tex} atom per unit cell =  6 x {tex}\frac{1}{2}{/tex} =  3 atoms

{tex}\therefore{/tex} Total number of atoms per unit cell                               =   4  atoms