This book focuses mostly on properties, several types such as (i)metal oxide ferrites, (ii) oxide with a shell, (iii) metallic, (iv) metallic with a shell, method of synthesis by precipitation from solution, co-precipitation, thermal decomposition, hydrothermal, microemulsion, polyol, chemical vapor deposition, laser pyrolysis, spray pyrolysis, and sonochemical methods and their current trending applications such as biomedical application, cancer theranostics, imaging, drug delivery, biosensing, environmental and agriculture applications of MNPs. The facture protectives for magnetic nanomaterials in various filed also summarized.