Cell, one of Dr. Gero's greatest creations. He is a creature who was formed from the genetic material of the most powerful
             warriors known at the time of his creation. Such warriors are Goku, Vegeta, Freeza, King Kold, Piccolo, and many more.
             Because of the fact he was formed from these fighters he is also able to do their moves such as; Goku's Kame-hame-ha,
             Piccolo's regeneration ability and his Makkankosappo (special beam cannon), Tienshinhan's Taioken (solar flare), etc. Making
             him the ultimate fighting machine. Please stop reading here if you do not want to spoil the episodes for yourself.

                 Cell actually didn't come from the DBZ timeline that is shown because the lab the un-developed cell was in became
             destroyed, he didnt even come from Future Trunks timeline (the Future Trunks that we know of), he came from a completely
             different timeline where Trunks beat the androids. In this timeline this was a big problem for Cell because he needed to
             absorb Android #17 and #18 in order to become "Perfect" and be the ultimate fighting machine. He killed Trunks and took
             the time machine that Trunks used in his time line (it's honestly too difficult to explain). Turning himself back to a previous
             state in his development (an egg like form) so he could fit in the machine, he traveled back in time to the timeline that we
             know of to a few years before Trunks arrival.

                 Cell gave re-birth to himself over time and hatched. He quickly brought himself to the form he was at before the time
             travel. The Z Warriors discovered the remnant shell(s) and were very confused. Cell began going to various places around
             the country/world causing panic by taking finding people and by using his tail he absorbs their life energy to become
             stronger. Piccolo after merging with Kami found Cell by accident from sensing Goku's ki (ki means energy) and many other Z
             Warriors ki all in the same spot. After fighting a little while with Piccolo, Cell learned how much stronger Piccolo was than
             himself. He knew winning was impossible and used a Taioken (solar flare) to escape. Now for any other enemy in DBZ
             before this point it wouldn't of worked but Cell could lower his ki just like any other DBZ character making him difficult to
             find and catch. So Cell continued on his path of destruction and whent to more cities gathering extra energy.

                 When Cell learned (sensed) Piccolo's fight with Android #17 he quickly whent to the battle where he easily beat both
             Piccolo and #17 (he was much stronger now because of all the people he absorbed). Cell absorbed Android #17 and
             transformed to a new level of power and physical appearance (his second stage). Tienshinhan happened to be there and
             used a force blow attack (the name eludes me so if someone out there reading this remembers the name of the attack please
             contact me). The attack essentially detains Cell for Android #16 and #18 to escape from Cell so #18 wont be absorbed. Goku
             recently recovered knows he can't fight Cell but he can't wait for Trunks and Vegeta to leave the room of spirit and time,
             Goku teleports himself there and gets Tien and Piccolo out and back to Kami's tower.

                 Cell continued to search for #18 but after Vegeta and Trunks got out of the room of spirit and time he stopped to fight
             Vegeta. Vegeta easily beat him down but Cell convinced Vegeta to let him absorb #18. Cell whent into his "Perfect Form"
             and became extremely poweful. He fought Vegeta again and knocked him out. Trunks too tried to fight Cell but was
             unsuccessful. Since Cell was now in his Perfect Form it was all just a game to him....Litterally and set up the Cell games. He
             gave all the warriors time to train while he waited.

                 Goku tried very hard to defeat Cell at the games and even though with all his training Goku was unable to win. Goku
             transfered the fight over to his son, Gohan. Gohan tried hard to fight but was on un-equal ground with Cell. When Cell
             learned of Gohan's possible hidden power through anger he wanted to trigger it so he released the "Cell Jr's" from his body
             and had them attack the Z Warriors and told them to kill them if they wanted. When #16's android's head was thrown over to
             where Gohan was by Mr. Satan, #16 asked Gohan to protect the animals etc. that he loved so much. Cell walked over and
             crushed the head of #16. Pushing Gohan two steps over the edge.

                 Gohan whent Super Saiya-jin level two and destroyed the Cell Jr.'s. Gohan fought Cell and when he learned he couldnt
             defeat Gohan so he decided to self destruct. When all looked hopeless Goku remembered his teleportation ability and
             transported Cell away from the earth and Goku was killed and it appeared as though it killed Cell also. But one of Cell's
             cell's(sounds wierd but it's true) survived and Cell returned to earth even stronger than he was before. Nevertheless, Cell
             was defeated by Gohan in a large Kame-hame-ha battle. Concluding the Cell Saga which is considered to be one of the best
             if not THE best saga in DBZ with it's constant twists of the plot line, keeping the viewers interested.