The nucleus has double layered membrane called the nuclear membrane.Nuclear membrane has pores which allows the transfer of material from inside the nucleus to its outside i.e cytoplasm.
Nucleus contains chromosomes which are visible as thread like structure only when the cell is about to divide.The chromosomes contains information for inheritance of features from parent to children in the form of DNA (deoxyribo nucleic acid)molecules.The chromosomes are composed of DNA and protein.The DNA contains all the necessary information for constructing and organizing the cell.The functional segments of DNA are called genes.When the cell which is not dividing the DNA is present as the part of chromatin material.The chromatin material is visible as entangled mass of thread like structure.When the cell is about to the chromatin material gets formed inside the chromsomes.
The nucleus plays an important role in cellular reproduction(the process by which a cell divides to form two new cells).It also plays a crucial role along with the environment by determining the way the cell will develop,in what form it will exhibit at maturity by directing the chemical activites of the cell.
The nuclear membrane separates all the contents of nucleus from its external environment