Illustrator Blend Tool does the trick of creating smooth transition between objects. You can blend open paths to create line effects and blend shapes to create realistic shadings. There are many creative things you can do with the Blend Tool and you will definitely be using it a lot in your illustrations.
Here are some quick interesting stuff you can do with blending.
With smooth blends you can create realistic shading which cannot be done with gradient.
You can create nice abstract blending line waves using Blend Tool. This is done by blending a dark to a light blue line.
With blend tools you can quickly align objects with specified steps.
This is a quick diagram of how a blend looks. A blend needs at least 2 objects to blend. The start object will blend to the end object with the amount of steps you specified for the blend. In this case, I set it to 3 steps. A spine will also be automatically created. This spine determines the path the in between objects take.
Method 1: Using Blend Function
To quickly make a quick smooth blend. Select the 2 objects you want to blend and go Object>Blend>Make. A smooth blend with be created.
Method 2: Using the Blend Tool
Another method I always use, is using the Blend Tool to do the job. I can have more control on the anchor points to blend to.
First select the start object.
Select the Blend Tool.
First click on the anchor point your want the blend to start.
Next, hold Alt/Option as you click the second anchor point you want it to blend to.
A Blend Options window pops up. Choose Specified Steps and enter 3 for the value.
The final blend will have the star morph to the final star in 3 steps.
To quickly change a smooth blending object to specified steps, Alt/Option click on the blending objects with the Blend Tool. The Blend Options pops up. Set the Spacing to Specified Steps.
At times, you may want to edit the path of the spine to a curve path instead of the default straight path. To do this, you can edit the path directly with the Pen Tool. Another cleaner way to do this is to draw the path of the spine. Select the new path and the blend object. Go to Blend>Replace Spine to replace the spine.
If you need to break the blend into individual objects. You can go Object>Expand to expand the objects. You can then edit the in between objects.