The former Research Laboratory for Crystal Physics continues the growth and defect structure investigation of nonlinear optical single crystals in a new organization, as a part of the Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences. The aim of the activity is to prepare specific crystals for basic and applied research as well as for applications. We improve the quality or modify the properties of well known nonlinear oxide and borate crystals and develop new materials. The principle nonlinear optical crystals in our profile are the followings: Paratellurite (TeO2), congruent, Mg-doped and stoichiometric lithium niobate (LiNbO3), a variety of sillenite structured crystals (Bi12MeO20, Me=Si, Ge, Ti, etc.), bismuth tellurite (Bi2TeO5) and nonlinear borates (BBO-beta-BaB2O4, LBO-LiB3O5, LTB-Li2B4O7, CLBO-CsLiB6O10 and YAB-YAI3(BO3)4). Details of the crystal preparation and the major achievements are discussed in the paper.