We actually can. There are microscopes that are able to see atoms, and even manipulate them. There are famous pictures of a quantum corral (you can google it) or a movie “A boy and his atom” (you can google it too) that used a microscopy technique called “Scanning Tunneling Microscopy” to manipulate atoms and observe them.
Other microscopes such as Transmission Electron Microscope use electrons to observe materials and they also can see atoms.
They’re really, really, super small! They’re about a million times smaller than the diameter of a single hair on your head. Our eyes can’t see things on such a small scale. We need special tools that Juan mentioned – which are really expensive and quite big! – to be able to take pictures of them.