First Step

Make a new document with a big size (I'd prefer 600x501), though you can do any size.

Now press "D" to go back to your default colors (black and white.)

Then press "X" to bring your foreground color to white.

Now press "Ctrl+Backspace." It will bring the whole thing black

It should look like this.

Second Step

Press "B" to go to your brush tools

Then select a brush size that's not too big and not too small.

Now to change your brush size, click the "Brush Dynamics" button on the very right of the brush options. (I use photoshop version 4.0, so if you don't have 4.0, well I don't really know the solution)

Now put it to these options

Spacing: 25%
Fade: 25
Hue jitter:0%
Hardness: 0 %
Scatter:0 %

Now take a brush size, not too big not too small of the size of your document. Now brush on the middle. Remember to make the foreground color white.

It should look similar to this.

Step Three (Easy Step)

Go to Filter>Distort>Twirl

Put it to this option

Angle: 999

It should look like this

Step Four

Time for the colors

Go to Layer>New Fill Layer>Gradient

Set the mode to Soft light (THIS IS VERY IMPORTANT)

Now select your favorite gradient.

After that make the style,angle, and scale anything you want for the gradient fill, but remember to pick "Align with Layer"

Mine looks like this

Step Five

Flatten your image by going to Layer>Flatten Image

We flattened the image so we could do a very unique thing

Go to Filter>Distort> Polar Coordinates

Now choose Rectangular to Polar and press ok

Do you see a straight line on the middle of it? Well we can fix that easily with the smudge tool

Select the Smudge tool and put it to these settings

Size: 40
Mode: Normal
Strength: 48

Now start smudging where you see the lines.

Now there are no more lines

This is what mine look liked

Step Six

This is a very important step!

Follow Step Five again, but without flattening your image. ( If you don't see any lines do not smudge tool)

We do this to make the image more better

This is what mine looks like

Last Step

This step will make liquid effect

Ok now go to Filter>Distort>Wave

Put these settings (Optional) (You don't have to follow my settings, be creative and do your own settings ^^)

Number of Generators: 1

Wavelength

Minimum:169
Maximum: 169

Amplitude

Minimum: 197
Maximum: 500

Scale

Horizontal: 73
Vertical:55

Remember to make the wave type "sine."

Now keep pressing randomize until you like the liquid effect

Mine looks like this

Done!