He said to him, "Most assuredly, I tell you, hereafter you will see heaven opened, and the angels of God ascending and descending on the Son of Man."
This first sub-section in the body of the fourth Gospel (John 1:19-51) contains the prelude to Jesus’ public ministry. [Note: See Stephen S. Kim, "The Relationship of John 1:19-51 to the Book of Signs in John 2-12," Bibliotheca Sacra 165:659 (July-September 2008):323-37.] John stressed John the Baptist’s witness to Jesus’ identity, first in a veiled manner and then openly. Then he recorded the response of some of John’s disciples, which was to follow Jesus. Philip’s witness resulted in Nathanael’s declaration of faith in Jesus, limited as it may have been, and Jesus’ claim to be the revealer of God and the way to God. The "greater things than these" that Jesus promised (John 1:50) follow providing an even more solid foundation for faith in Him (cf. John 20:31).