When I had to replicate the 80's lava lamp object, my first thought, was to create a complex particle system, and use the drawing api to draw a gradient simulate the plasma effect, but after a while, I found that using blendModes,combined with gradient colored circles, simplify the problem to the limit.

Blend modes are conceptually very simple, but their practical application is sometimes difficult to see, and really often does result only from a bit of luck and guesswork.

( A biological texture generated with blend modes )

So what exactly is a blend mode?
In simple words, a blend mode is a setting on a display object that alters the color of each individual pixel based on the color of the visible pixel below it.

Items like Sprite, Shape, Bitmap, or TextField can each get their own blend mode setting.

Lets see the most simple of all, "Add" blend mode.
The pixel values of the display object and the background are added together, with a limit of 255 applied.

If our background is then medium gray color (0x666666) and our object is red (0xFF0000) the result will be a lighter red (0xFF6666).

Let's go back to the plasma simulation.

Let's create a new Sprite, or movieClip, and draw a gradient circle from white to transparent black, with a size of , for example 200×200 pixels.

If we add more sprites to the stage, we will have something like this.

But if we set now our blendMode to add, the gradient colors will add to the background, and relatively dark areas intersecting our three sprites, will now look brighter, creating the plasma effect.

Finally, giving some color to the gradient, and adding movement to our particles, the effect will look like this.

Click here to see the demo. ( Requires Flash )

In a similar way, if we draw a black to white gradient circle, like this:

and we add it around the screen with random size and position, using blendMode "darker", (who will get the darker color of the two colors from a display object and the background) the resulting effect, if we apply a green color overlay, can simulate a biological texture like this:

Click here to see the demo. ( Requires Flash )

Flash has 14 blend modes, that can be combined to create different effects.

Playing with blendMode and different figures, can create random images with no work, but a loot of power.