We live in an exciting time for science. Experimentally techniques have advanced to the point that some fundamental concepts, long predicted but never before seen directly, can be visualized. Three examples come to light recently:
As you can find in any quantum mechanics textbook, the way electrons orbit around an atomic nucleus is not (as sometimes explained) like a planet circling a star, in the sense that the electron does not have a definite position at any specific point in time. Rather, the electron exists in an orbital, which indicates the probability of finding the electron at each point. Such an abstract and counter-intuitive concept might seem beyond any attempt to demonstrate directly. Some have even claimed that orbitals are just a kind of mathematical slight of hand, useful for calculation but not corresponding to anything “real.” But recently, the electron orbitals of a hydrogen atoms have been visualized, using a clever technique that takes advantage of the interference pattern of the electron with “itself” when it is ejected from the atom by a strong laser.
Another surprising prediction of quantum mechanics is the possibility of “entanglement,” in which the state of two particles cannot be expressed by describing each independently. Instead, information about one is entangled with the other, and making a single measurement gives you information about both simultaneously. For example, imagine a photonic crystal that emits two photons, but always in such a way that the polarizations are the different (if one photon is polarized up and down, the other is polarized at a 45 degree angle, or vice versa). Measuring one photons will instantly change the state of the other in something that Einstein called “Spooky action at a distance.” Entanglement has been shown many times before, but a new video has been made showing the effects in real time. Sean Carroll has a good explanation.
Lastly, but probably most amazingly, scientists have been able to directly observe the atomic bonds inside a molecule using an atomic force microscope.
In order to obtain such sharp resolution, a single carbon monoxide atom was attached to the end of the cantilever tip, and the deflection created by the electron density of the chemical bonds was measured by shining a laser on the tip.
What is amazing is that all of these experiments agree with predictions made decades ago, although if you asked scientists then, they would likely have been very skeptical that these predictions could have been confirmed so vividly.