The Androids Saga is broken up into four sub-arcs:
Original Japanese: from volume 28 Dragonball Z: volume 12. Trunks, son of Vegeta and Bulma, arrives from the future. After killing the redivivus Freeza, he warns Goku and the rest of the Z-Fighters of the imminent coming of two deadly Androids built by the Red Ribbon Army.
Androids: First Wave
Original: 29 DGZ: 13. Android n° 19 and Android n°20 (Dr. Gero) launch their attack, but they'are easily stopped. Gero then activate his two other androids.
Androids: Second Wave
Original: 30 DGZ: 14. Androids n°17 and Android n° 18 activate n°16 and after defeating the Z-Fighters they got on the trail of Goku to kill him.
Original: 30 to 32 DGZ: 14 to 16. Cell appears to confront the Z-Fighters and hunt down the two renegade Androids, becoming stronger and stronger in the process.
The Cell Games
Original: 32 to 35 DGZ: 16 to 19. After gaining his perfect body, Cell organize a fighting tournament for his own amusement. Gohan ends up being the one who finally defeats him.