Steroid receptors are evoluted from the common ancestor and have the same structure as steroid receptor superfamily. The nuclear receptors are characterized by a central DNA binding domain with specific DNA sequences known as hormone response element, ligand binding domain in the C terminal and N terminal domain with the tissue specificity. Nuclear receptor superfamily is divided into four classes based on the dimerization and DNA binding properties, homodimers as steroid hormone receptor, heterodimers with RXR, homodimers and monomers. Most of orphan receptors fall into the last 2 classes. The coregulators as coactivators and corepressor are determined. The mechanism of action of nuclear receptor on chromatin in the nucleus are clarified precisely from the stand point of the clasters of coregulators and the complex of nuclear receptor and coregulators. The crosstalk of nuclear receptor and peptide hormone signal in the cell is important in the autocrine and paracrine action. Non-genomic action of steroid hormone is also proposed.