The present work investigates PMMA colloids in a polymer matrix of linear chains as a simple and suitable system for complex nanocomposites. The investigation was based on SANS experiments, which were enabled by the use of deuterated colloids immersed in a matrix of linear hydrogenated chains. Cross-linked deuterated PMMA-colloids were synthesized with two different sizes (70 and 140 nm) by means of the surfactant-free emulsion polymerization method and the swelling behavior adjusted by varying the amount of added cross-linker (1.5 and 15.0 mol-%) at each size respectively. Colloid−polymer blends were prepared from colloid−polymer solutions. SANS experiments on these blends consistently revealed that colloids with a low cross-linking density could be homogeneously distributed throughout the matrix of linear chains. Fits with model form factors indicated the structure of fuzzy spheres for these molecularly dispersed microgels, which are slightly swollen with respect to their size and shape in H2O. Contrary to this, colloids with a high cross-linking density form aggregates in the blends. Despite this aggregation, we succeeded to unravel the shape and the size of single colloids by preparation of colloid− polymer blends where the colloid component is a binary mixture of deuterated and hydrogenated colloids both with a high crosslinking density. SANS on the latter blends suggested a core−shell particle in a lattice cell of an aggregate.