The main structure of epidermis is composed of 4 layers or strata. From bottom to top, these are:
stratum basale attached to the basement membrane.
two intermediate layers (stratum spinosum and stratum granulosum), and
at the top is stratum corneum.
There is also a 'thick skin' or the fifth stratum present at the feet and palm, known as stratum lucidum. It is present between the stratum corneum and the stratum granulosum.
Stratum basale is the deepest layer attached to the basement. Stratum spinosum makes the skin strong and flexible. Stratum granulosum prevents water loss from the body. Stratum corneum acts as a protective barrier on the outermost side of the skin. Stratum lucidum is made up of dead cells present only in thick skin.