For a next pitch drop to drop. This is the famous pitch drop experiment, about which I found out on Radiolab. You might think there is nothing so exciting about watching pitch to drop, but the funny thing is that since the start of the experiment in 1927 it had dropped only 8 times, and to date, no one has ever witnessed a drop fall. So it becomes a really thrilling thing to observe!
Link to webcam. Be the one who witnesses the pitch drop fall!