Semiconductor microdisk resonators have received considerable attention over the past several years due to their novel approach of using total internal reflection of light in the cavity to create whispering gallery modes. Traditionally, microdisks have been fabricated using a top-down approach, utilizing either dry or wet etching to create the desired size and shape of the microdisk. Here we report the fabrication of hexagonal ZnO microdisks using a bottom-up approach. ZnO microdisks are grown in aqueous solutions of zinc nitrate and ammonium hydroxide. In addition, sodium citrate is added to the solution to slow the growth of the zinc oxide in the vertical direction. The creation of microdisks using a bottom-up approach allows for ease of fabrication, little waste of material, and the ability to implant structures into the microdisk and continue the growth process. Zinc oxide is a wide bandgap (~3.3eV) semiconductor with a large exciton binding energy (~60meV) making it a desirable material for optoelectronic devices. Here we present the fabrication process of our hexagonal ZnO microdisks and several scanning electron microscope images of ZnO microdisks with various growth parameters, including the concentration of both the zinc nitrate and sodium citrate in the solution as well as the growth time. Using our novel approach, we are able to create an undercut in our microdisks without the use of etching. In addition, photoluminescence spectroscopy is performed to investigate the optical characteristics of the ZnO microdisk cavities. The results obtained from photoluminescence spectroscopy are compared with finite difference time domain (FDTD) simulations to design and optimize the microdisk structure and determine the modes of the resonator and the maximum quality factor of these modes. Overall, we demonstrate the ability to grow zinc oxide microdisks in solution and by varying various parameters change the size of the disks. This novel approach in the fabrication of microdisks presents many advantages over the traditional approach and allows for the possibility of incorporating numerous structures (e.g. quantum dots or nanodiamond) into the microdisks during growth which is difficult with other fabrication techniques. In addition, FDTD simulations and photoluminescence spectroscopy measurements allow us to better understand the quality of the ZnO microdisk cavities we have created and the optical properties of the ZnO that we are growing. Current work is focused on further characterizing and optimizing the conditions for formation of the microdisks, by detailed optical characterization of the structures, as well as developing better control over the shape of the resonators.