Process of embryo implantation into uterine mucosa consists of two stages. What is morphological evidence of first stage?

Process of embryo implantation into uterine mucosa consists of two stages. What is morphological evidence of first stage?

1.  Destruction of endometrial connective tissue


2.  Destruction of endometrial epitheliocytes


3.  Increase of uterine gland secretion


4.  Decrease of uterine gland secretion


5.  *Blastocyst attachment to endometrium surface