I was wondering how you would create something like this:
As you can see, there is a shadow in the bottom left, which gets lighter as you move diagonally to the top right. There is also a fleck of white added, which is very easy to apply.
I had a go myself, using a linear gradient, with about 75% opacity either side and nothing in the centre. It didn't work!
It's fairly easy to recreate the bevel effect. The inner swirl is a bit more difficult.
I created the swirl with several variations of
Filter > Render > Clouds set to
Multiply and then merged with a solid color. Then used
Filter > Oil Paint... to add some additional swirl variations. And finally
Filter > Distort > Twirl and
Filter > Blur > Radial Blur to create the twist appearance.
I did this on a couple layers and used some blending between the layers to add some depth to the overall swirl effect.
From there it's a fairly simple matter to use
Layer > Layer Style > Bevel & Emboss... and adjust settings to create the shine and shadow of the "button" effect. I actually used two layers for the Bevel & Emboss (with the Fill Opacity set to 0% so only the effect shows through) and used color burn and screen on one and multiply and screen on the second.
This isn't perfect, but your original image was a photograph of a drop of what appears to be fingernail polish with the bevel layer style added to the photo. It wasn't created entirely in Photoshop. You could simply photograph a drop of fingernail polish yourself, then ad the bevel effect to enhance the depth as someone did to your sample image.
You could also overlay a photo on top of any creation to add some appearance with that....