A method for controlling polymer morphology in olefin polymerization, comprising: flowing a catalyst through a first concentric flow path of the injection nozzle having two or more concentric flow paths and into a fluidized bed disposed within a reactor; flowing a first amount of feed comprising one or more olefins, one or more inert fluids, or a combination thereof through a second concentric flow path of the injection nozzle at first flow rate and first temperature and into the fluidized bed; and contacting the first amount of feed with the catalyst within the fluidized bed at conditions sufficient to produce a polyolefin having a first size distribution; flowing a second amount of the catalyst through the first concentric flow path and into the fluidized bed; flowing a second amount of feed comprising one or more olefins, one or more inert fluids, or a combination thereof through the second concentric flow path at a second flow rate and a second temperature and into the fluidized bed; determining the weight % of fines and contacting the second amount of feed with the catalyst within the fluidized bed at conditions sufficient to produce a polyolefin having a second size distribution, wherein the first size distribution is different from the second size distribution, wherein the first temperature is different from the second temperature and/or the first flow rate is different from the second flow rate; wherein an increase from a first temperature to a second temperature and/or increase in the flow rate of the feed from a first flow rate to a second flow rate increases the percent of polymer product fines by at least 1% based on the weight % of fines produced at the first temperature or the first flow rate; or wherein a decrease from a first temperature to a second temperature and/or a decrease in the first flow rate to a second flow rate reduces the percentage of polymer product fines by 2% to 75% based on the weight of fines produced at the first temperature or the first flow rate. flowing a catalyst through a first concentric flow path of the injection nozzle having two or more concentric flow paths and into a fluidized bed disposed within a reactor; flowing a first amount of feed comprising one or more olefins, one or more inert fluids, or a combination thereof through a second concentric flow path of the injection nozzle at first flow rate and first temperature and into the fluidized bed; and contacting the first amount of feed with the catalyst within the fluidized bed at conditions sufficient to produce a polyolefin having a first size distribution; flowing a second amount of the catalyst through the first concentric flow path and into the fluidized bed; flowing a second amount of feed comprising one or more olefins, one or more inert fluids, or a combination thereof through the second concentric flow path at a second flow rate and a second temperature and into the fluidized bed; determining the weight % of fines and contacting the second amount of feed with the catalyst within the fluidized bed at conditions sufficient to produce a polyolefin having a second size distribution, wherein the first size distribution is different from the second size distribution, wherein the first temperature is different from the second temperature and/or the first flow rate is different from the second flow rate; wherein an increase from a first temperature to a second temperature and/or increase in the flow rate of the feed from a first flow rate to a second flow rate increases the percent of polymer product fines by at least 1% based on the weight % of fines produced at the first temperature or the first flow rate; or wherein a decrease from a first temperature to a second temperature and/or a decrease in the first flow rate to a second flow rate reduces the percentage of polymer product fines by 2% to 75% based on the weight of fines produced at the first temperature or the first flow rate.