Image source. (Fair warning, many image source links will be spoilers.)
I'll start with one of popular science's hottest topics right now-- for most of you, it might be clear from the grid shape, but I'll leave you to figure it out.
I constructed this puzzle on paper (leaning heavily on XWord Info), so it's only available in PDF format. The grid has color, but don't worry if you only have access to a B&W printer-- the contrast still shows up.
I'll be honest-- grid-wise and fill-wise, this was one of the greatest challenges of my crossword career. I know it isn't perfect, but it certainly redefined what I thought was possible in a puzzle, and I hope it does for you too.