Of course, to some degree this is philosophical - what is a "real" image? But I'm not aware of anyone claiming to have made a meaningful image of anything smaller than single atoms. From
a nice discussion of this kind of thing in Discover:Currently, the smallest atom scientists can see is lithium, number 3 on the periodic table. The next milestone is to push the resolution below the Bohr radius, about half an angstrom. At that level, even the tiniest atoms—hydrogen and helium—come into view. “That may take a couple of years,” Pennycook says. The ultimate dream is to take STEM into three dimensions with confocal electron microscopy, which images a material in slices by changing the focus of the beam. Pennycook and others have made major strides in this direction, and 3-D pictures of individual atoms are already becoming available. “This is a historic time,” says Pennycook. “Only once do we pass that threshold of being able to see atoms.”
Yet physicists know they are also approaching a wall. “We’re getting close to the fundamental limit due to quantum zero energy,” Pennycook notes. In quantum mechanics, every particle is a little blurry because it always carries a minimum iota of energy—the so-called ground state energy. Cooling the sample to ultralow temperatures helps slow the atoms down, but they will never sit perfectly still for the camera. “You can cool the atom, but you’ll never stop it entirely,” Pennycook says. Physicists expect STEM to bottom out at around one-tenth of an angstrom. No matter how much our technology improves, on some level atoms will always remain invisible.
Beyond the STEM image lies only the imagination. In poet Muriel Rukeyser’s words, “The universe is made of stories, not of atoms.” Physicists have laid bare the atomic domain, and what we will never see is as meaningful—and beautiful—as what we can.
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