According to the latest information we got
String theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings.
We know that anything we've ever seen on a microscopic level or a gigantic level that matter has thickness? let it's thickness be 1.6 x 10-35 m (Plank length) or let it be 1 m , It has some thickness. Right?
So everything we've seen is 3-dimensional right? no matter how much we zoom , we get protons that have thickness.
So if matter has thickness then how can we say that Something is "1-dimensional".
Anything that's 3D is made up of something 3D. If we add 0 thickness we get 0 thickness but if we add some thickness like atoms and molecules we get 3D matter as the constituents have thickness.
Then how particles of particle physics are replaced by one-dimensional objects called strings?