Genesis 28:12 & 13a
"He had a dream in which he saw a stairway resting on the earth, with its top reaching to heaven, and the angels of God ascending and descending on it. There above it stood the Lord, and he said: 'I am the Lord, the God of your father Abraham and the God of Isaac.'" NIV translation
Jacob had a dream in which he saw what has been commonly called "Jacob's ladder" but the Hebrew word is "cullam" and it is more accurately described as a staircase.
He saw angels, which are messengers from God, going up and down the stairs with God at the top. He knew that it was God as He identified Himself as the God of his father and grandfather.
How wonderful it is to see that, during his first time alone and feeling scared, God showed up to reassure Jacob that he was not alone. So, why would God show Jacob a staircase? A ladder or staircase provides access to a higher place and, in this case, God was demonstrating the fact that He was active in the world through His messengers. Although this is a rather routine idea for us, as believers, it would have been an amazing revelation to Jacob.
We also notice that Jacob saw the angels going both up and down the stairs and that is a reminder that angels are simple messengers who take their orders from God. It seems that everyone in our world, today, believes in angels but sometimes they are elevated to godlike status and that is wrong. They, like us, are created by God and it is God alone that deserves our worship.