This was created in illustrator quite simply. The designer made a number of different sized circles using the shape tool and then chose a number of different colors. They used the fill tool to change the color of the shapes. Then they changed the opacity of each circle so that some appear more transparent than others. The text colors are the same as some of the dots, so everything works together.
This picture is very creative and apply the simple use of illustrator. Though it uses only bubbles, , it changes opacity, shape and color. The designer uses its intelligence to put circles in different positions and make the whole picture look quite colorful and creative.