Although there are many distant things in our universe that we can't seem to explain with science, there are also things all around us that are within reaching distance that science still has trouble explaining.
For example, our own bodies, which we interact with on a daily basis, do a lot of strange things that we just can't seem to fully explain. Beyond Science details just a few of them (six to be exact): hypnic jerk, sudden sneezing, the placebo effect, yawning, blushing, and sleep.
You may have experienced, one, some, or all of these phenomena; most people do. Many of these phenomena have nothing but theories to explain their existence, but no concrete explanations have been proven to suggest why they occur.