cis-trans

Two molecules, each with a carbon double bond at the centre (it looks like o=o). Each carbon atom has a yellow and a green molecule attached to it. The one on the left is a cis molecule and both of the yellow molecules are on the top and both of the green molecules are at the bottom. The one on the right is a trans molecule and has one yellow and one green molecule at the top and one green and one yellow molecule at the bottom