Butterflies formed by a random pattern of dots.

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1

Create a new 1024x768 pixels document with a black background.

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2

Duplicate the current layer (Ctrl+J).

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3

With the new layer selected, use the "Add Noise" filter (Filter> Noise> Add Noise) to apply the following properties: Amount: 3.5% Distribution: Uniform Click OK.

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4

Use the "Threshold" tool (Image> Adjustmets> Threshold) and drag the input slider left so that it hits the very first pixel of the histogram.

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5

Use the "Magic Wand" tool (M) to select the black areas of the layer, clear (Delete) and deselect (Ctrl+D).

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6

Add a layer mask with a black background to the current layer (Layer> Add Layer Mask> Hide All).

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7

With the layer mask selected, use the "Brush" tool and select the "Butterfly" brush (Special Effects Brushes) and paint.

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8

Apply an "Outer Glow" layer style (Layer> Layer Style> Outer Glow) to the current layer.

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9

Use different layer styles and properties to get different effects.

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10

Here is a cropped area of a high resolution version.