What caused the tension in kansas and nebraska

The issue in Kansas and Nebraska started when Stephen Douglas askes for Kansas and Nebraska to be added into the Union as states. southerns did not agreed with this since these states would become free states because of the Missouri Compromise and therefore the house of Representatives would now have more delegates from the free states than from the states that supported slavery. To solve this Congress passed the Kansas-Nebraska Act which gave those states the right of popular sovereignty, which means that the population from those states would be able to decide by themselves whether they wanted to be free or slaved states. When this happened, groups of people that supported the abolitionist movements and groups that supported slavery moved into those states and started fighting to gain control of the states, there before creating all the tension and what is called Bleeding Kansas