1. Hidden rainbows made their Instagram debut and people were obsessed.
2. Oil-slick hair was perfect for brunettes who wanted something a little *different*.
Don't want to bleach your hair completely to get the rainbow look? Then meet your match.
3. And then there was ~sun bun~, a new tie-dye technique developed by hairstylist Harriet Muldoon.
4. Metallic hair was major in 2016, especially after Guy Tang launched his metallic hair dye line.
You'll be completely mesmerized by it after watching his videos.
5. Subtle rose-mauve hair was a fall favorite.
Stylist Hannah Edelman mixed colorful hues with warm browns to achieve this gorgeous color.
6. Holographic hair was beautiful and psychedelic all at once.
7. Colorful undercuts were like hidden works of hair art.
8. Hair marbling has been around for a while, but in 2016 we've seen more of it with gorgeous colorful tones.
9. Half-and-half hair came through for the people who can't make up their minds.
It's also reminiscent of Harley Quinn.
10. Watermelon-inspired hair came out of nowhere to make our Instagram feeds feel like summer year-round.
11. While straight-up rainbow hair still stunned.
12. The balayage technique was still very present in 2016, but this time we saw a little more color and a little less blonde ombré.
14. And neons made a much-needed comeback.
15. We learned about stunning *unicorn curls*.
See more beautiful photos from Amina Mucciolo's hashtag here.