diff --git a/src/node/functions.rs b/src/node/functions.rs
new file mode 100644
index 0000000..dc55816
--- /dev/null
+++ b/src/node/functions.rs
@@ -0,0 +1,10 @@
+pub fn sine(inputs: Vec<f64>) -> f64 {
+    inputs[0].sin()
+}
+pub fn sum(inputs: Vec<f64>) -> f64 {
+    let mut sum = 0f64;
+    for i in inputs {
+        sum += i;
+    }
+    sum
+}
diff --git a/src/node/mod.rs b/src/node/mod.rs
index b88873f..ed5fd31 100644
--- a/src/node/mod.rs
+++ b/src/node/mod.rs
@@ -1,6 +1,7 @@
 use crate::node::node_modifier::NodeModifier;
 use handler::*;
 
+mod functions;
 mod handler;
 mod node_modifier;
 
diff --git a/src/node/node_modifier.rs b/src/node/node_modifier.rs
index 19dcfb3..5f8fd33 100644
--- a/src/node/node_modifier.rs
+++ b/src/node/node_modifier.rs
@@ -1,15 +1,35 @@
 use crate::node::Node;
+use crate::node::functions;
+use crate::node::handler::NodeHandler;
 use rand::random_range;
 
 const PICK_STOP_PROBABILITY: u8 = 2;
 
 pub struct NodeModifier<'a> {
     picked_node: &'a mut Node,
+    function_mutation_pool: Vec<fn(Vec<f64>) -> f64>,
+    number_mutation_pool: Vec<fn(f64) -> f64>,
 }
 
 impl<'a> NodeModifier<'a> {
+    fn get_standard_pool() -> (Vec<fn(Vec<f64>) -> f64>, Vec<fn(f64) -> f64>) {
+        let standard_function_mutation: Vec<fn(Vec<f64>) -> f64> = vec![functions::sine];
+        // *4, /4, *2,
+        let standard_number_mutation: Vec<fn(f64) -> f64> = vec![
+            |x| x * 4f64,
+            |x| x / 4.0f64,
+            |x| x * 2f64,
+            |x| x / 2.0f64,
+            |x| x + 1f64,
+            |x| x - 1f64,
+        ];
+        return (standard_function_mutation, standard_number_mutation);
+    }
     //Builders
-    pub fn from_random(root: &'a mut Node) -> NodeModifier<'a> {
+    pub fn from_random(
+        root: &'a mut Node,
+        custom_pools: Option<(Vec<fn(Vec<f64>) -> f64>, Vec<fn(f64) -> f64>)>,
+    ) -> NodeModifier<'a> {
         let mut selected = root;
         while random_range(0..PICK_STOP_PROBABILITY) == PICK_STOP_PROBABILITY - 1 {
             let len = selected.children.len();
@@ -18,12 +38,23 @@ impl<'a> NodeModifier<'a> {
             }
             selected = &mut selected.children[random_range(0..len)];
         }
+        let pools = custom_pools.unwrap_or(NodeModifier::get_standard_pool());
         NodeModifier {
             picked_node: selected,
+            function_mutation_pool: pools.0,
+            number_mutation_pool: pools.1,
         }
     }
-    pub fn from_node(node: &'a mut Node) -> NodeModifier<'a> {
-        NodeModifier { picked_node: node }
+    pub fn from_node(
+        node: &'a mut Node,
+        custom_pools: Option<(Vec<fn(Vec<f64>) -> f64>, Vec<fn(f64) -> f64>)>,
+    ) -> NodeModifier<'a> {
+        let pools = custom_pools.unwrap_or(NodeModifier::get_standard_pool());
+        NodeModifier {
+            picked_node: node,
+            function_mutation_pool: pools.0,
+            number_mutation_pool: pools.1,
+        }
     }
 
     pub fn add_node(&mut self, node: Node) {
@@ -38,5 +69,23 @@ impl<'a> NodeModifier<'a> {
         self.picked_node.children.insert(operated_index, node);
     }
 
-    pub fn mutate_node(&mut self) {}
+    pub fn mutate_node(&mut self) {
+        match self.picked_node.handler {
+            NodeHandler::Number { number } => {
+                self.picked_node.handler = NodeHandler::Number {
+                    number: (self.number_mutation_pool
+                        [random_range(0..self.number_mutation_pool.len())])(
+                        number
+                    ),
+                };
+            }
+            NodeHandler::Function { function } => {
+                self.picked_node.handler = NodeHandler::Function {
+                    function: self.function_mutation_pool
+                        [random_range(0..self.function_mutation_pool.len())],
+                }
+            }
+            _ => {}
+        }
+    }
 }