The first thing Obi-Wan experiences in his dream is not a vision, but an echo of Padmé Amidala's last words after giving birth.
The first thing shown in Obi-Wan's dream is the collapse of the control center on Mustafar where he and Anakin Skywalker dueled in the climax of Revenge of the Sith.
The next portion of Obi-Wan's dream shows a number of quick cuts from his duel with Anakin on Mustafar 10 years earlier.
The next portion of Obi-Wan's dream takes him further into the past, back to the death of his mentor, Jedi Master Qui-Gon Jinn, in The Phantom Menace.
The next portion of the dream recalls Obi-Wan and Anakin during a wild flying car chase on Coruscant from Attack of the Clones.
This portion of the dream ends with a quick cut of Anakin Skywalker, now more Darth Vader, on Mustafar
The third segment of Obi-Wan's dream opens with another echo from Revenge of the Sith, as he recalls Yoda's warning that "only pain will you find"
Again, Obi-Wan's dream flashes back to the death of the Jedi Master who trained him, this time seeing Qui-Gon Jinn being cut down by the Sith Lord Darth Maul.