Oil and water droplet photography is a very popular and easy exercise in macro photography. It is done with materials that you likely have around the house.  If you are interested in an explanation, there are photographs of the setup at the end of this presentation (scroll to the bottom), with details about how the images were obtained. I am usually strict with myself about only posting one or two best shots from a shoot or location, but I like these so much I couldn't choose.  I hope you enjoy them. Please let me know which are your favorites (use the "contact me" link, above).
Part One: Oil Droplets on Water

A galaxy far, far away

Shiny and Blue

Purple Sunset

Sunburst

Edge of the Bowl


Gradient with refractions


Part Two: Water Droplets on Oil

The Rainbow Within

The Embryo

Green Swirl

The Ice Cream Cone

Just Dots


Cut Glass Plate

The Glass plate

Colored water

As promised, here's how I made these images:
The Setup, Top to bottom
​​​​​​​Camera: Nikon D850 with Nikkor 105 mm macro and 20 mm. extension tube.
Vessel Containing oil/water mixture. 
Plexiglas Sheet on supported by piles of CD's.
Colored objects: construction paper strips, translucent Roscolux gels, iPhone photo.
Light Source: Light box or 1-2 rechargeable Litra flashlights, shined mostly on the background from an angle.
Light box: (mine is for reading old fashioned film X-rays).
Additional items: chopstick, eyedropper, remote shutter release, food coloring, various bowls and plates. 
The Process:
Oil Droplet Photos: I filled a vessel with a layer of water, and added canola oil and swirled it around to break up the globs. I combined different light sources, shining flashlights at different angles, little ambient light. That's not much light, so the exposures were long and I had to worry a lot about blur from vibration or the droplets moving.  The oil did an amazing job refracting light from the plate. I also found that by adding a little dish detergent to the mix, the bubbles became more stable and I could easily manipulate them with a chopstick. 
Water Droplet Photos: I placed a layer of oil in the vessel. I used food coloring to make dishes of colored water (see above) and used a dropper to drop water onto the oil. The droplets tended to swim around a lot and they also liked to merge with one another. I had to shoot quickly while this was going on. I used two flashlights, one to light them from below, and a less bright one to add a highlight above. My favorite is the one that looks like an embryo...the blue drop swallowed a smaller yellow drop leading to that interesting pattern. Some of the color in these photos comes from the droplets that burst, some from the background. 
The camera is in an awkward position, making it hard to look through the viewfinder or even at the LCD. It is helpful to either shoot tethered or use a wifi-camera app like NIkon Snapbridge and an Ipad.