What is the best solution for particle Characterization?

Particle characterization is the process of identifying various particles by particle shape, size, surface properties, charge properties, and structure. There is a broad range of commercially available particle characterization techniques that can be used to measure particulate samples. There are some techniques for all types of sample analysis:
Microscopy Image Analysis: The system comprises of a microscope, a digital camera and analysis software. A digital camera takes images of drug samples kept under the microscope and transfers to the connected computer. The software has unique algorithms to detect particles and calculate various parameters. It is a direct technique which measures 2D images of 3D particles. Image analysis gives a number-weighted distribution where each particle is given equal weighting irrespective of its size.
Laser Diffraction: Laser diffraction measures particle size distributions by measuring the angular variation in the intensity of light scattered as a laser beam passes through a dispersed particulate sample. Large particles scatter light at small angles relative to the laser beam and small particles scatter light at large angles. The angular scattering intensity data is then analyzed to calculate the size of the particles responsible for creating the scattering pattern, using the Mie theory of light scattering. The particle size is reported as a volume equivalent sphere diameter.
Dynamic Light Scattering: Dynamic light scattering (DLS), also known as Photon Correlation Spectroscopy (PCS) or Quasi-Elastic Light Scattering (QELS).This is an analytical technique used to measure the particle size distribution of protein formulations across the oligomer and sub-micron size ranges of approximately 1 nm to 1 µm.
Raman Spectroscopy: In Raman spectroscopy a laser is focused into the sample, the inelastic scattered radiation (Raman) is optically collected and directed into a spectrometer, which provides wavelength separation, and a detector converts photon energy to electrical signal intensity. The applications range from verification of raw materials to process monitoring of drug production to quality control of products. Similar to an infrared spectrum, a Raman spectrum consists of a wavelength distribution of peaks corresponding to molecular vibrations specific to the sample being analyzed.
Sieve Analysis: Sieve analysis is a technique used to determine the particle size distribution of a powder. This method is performed by sifting a powder sample through a stack of wire mesh sieves, separating it into discrete size ranges. A sieve shaker is used to vibrate the sieve stack for a specific period of time.
So, the best solution for particle characterization is Microscopy because it is clearly visible in size shape etc.