diff --git a/README.md b/README.md
index 22d340b..b8e3761 100644
--- a/README.md
+++ b/README.md
@@ -30,9 +30,10 @@ or
 ```bash
 yarn add react-style-stringify
 ```
+
 > [!NOTE]
 > This package uses the `CSSProperties` type from `@types/react`.
-> 
+>
 > If you're working with TypeScript and don't use React, install [@types/react](https://www.npmjs.com/package/@types/react).
 
 ## Usage
@@ -54,7 +55,7 @@ const cssString = stringifyCSSProperties({
   padding: 20,
   backgroundColor: "teal",
 });
-// Output: "flex:1; padding:20px; background-color:teal;"
+// Output: "flex:1;padding:20px;background-color:teal;"
 ```
 
 **Inject `!important` into CSS string**
@@ -68,7 +69,7 @@ const importantCssString = stringifyCSSProperties(
   },
   true
 );
-// Output: "flex:1!important; padding:20px!important; background-color:teal!important;"
+// Output: "flex:1!important;padding:20px!important;background-color:teal!important;"
 ```
 
 ### Convert a `Record<string, CSSProperties>` object
@@ -83,7 +84,7 @@ const cssMapString = stringifyStyleMap({
     padding: 10,
   },
 });
-// Output: "p{margin:0; color:teal;} #root ul.my-list > li{padding:10px;}"
+// Output: "p{margin:0;color:teal;}#root ul.my-list>li{padding:10px;}"
 ```
 
 **Inject `!important` into CSS string**
@@ -101,7 +102,7 @@ const importantCssMapString = stringifyStyleMap(
   },
   true
 );
-// Output: "p{margin:0!important; color:teal!important;} #root ul.my-list > li{padding:10px!important;}"
+// Output: "p{margin:0!important;color:teal!important;}#root ul.my-list>li{padding:10px!important;}"
 ```
 
 ## API
diff --git a/src/__tests__/stringifyCSSProperties.test.ts b/src/__tests__/stringifyCSSProperties.test.ts
index 97db107..92859b7 100644
--- a/src/__tests__/stringifyCSSProperties.test.ts
+++ b/src/__tests__/stringifyCSSProperties.test.ts
@@ -35,7 +35,7 @@ describe("stringifyCSSProperties", () => {
   });
 
   it("doesn't change string CSS-value", () => {
-    const expected = "color:teal; margin:20rem; padding:5px 10px;";
+    const expected = "color:teal;margin:20rem;padding:5px 10px;";
     const actual = stringifyCSSProperties({
       color: "teal",
       margin: "20rem",
@@ -47,7 +47,7 @@ describe("stringifyCSSProperties", () => {
 
   it("converts CSS-prop name from camel to kebab case", () => {
     const expected =
-      "margin-bottom:20px; background-color:teal; border-radius:30rem; font-family:sans-serif;";
+      "margin-bottom:20px;background-color:teal;border-radius:30rem;font-family:sans-serif;";
     const actual = stringifyCSSProperties({
       marginBottom: "20px",
       backgroundColor: "teal",
@@ -59,14 +59,14 @@ describe("stringifyCSSProperties", () => {
   });
 
   it("adds 'px' to numeric CSS-value", () => {
-    const expected = "margin:20px; padding:5px;";
+    const expected = "margin:20px;padding:5px;";
     const actual = stringifyCSSProperties({ margin: 20, padding: 5 });
 
     expect(actual).toBe(expected);
   });
 
   it("doesn't add 'px' to unitless CSS-prop and '0' CSS-value", () => {
-    const expected = "z-index:20; flex:1; opacity:0.5; margin:0; padding:0;";
+    const expected = "z-index:20;flex:1;opacity:0.5;margin:0;padding:0;";
     const actual = stringifyCSSProperties({
       zIndex: 20,
       flex: 1,
@@ -77,4 +77,19 @@ describe("stringifyCSSProperties", () => {
 
     expect(actual).toBe(expected);
   });
+
+  it("injects the '!important' statement for each style property", () => {
+    const expected =
+      "color:teal!important;margin:20rem!important;padding:5px 10px!important;";
+    const actual = stringifyCSSProperties(
+      {
+        color: "teal",
+        margin: "20rem",
+        padding: "5px 10px",
+      },
+      true
+    );
+
+    expect(actual).toBe(expected);
+  });
 });
diff --git a/src/__tests__/stringifyStyleMap.test.ts b/src/__tests__/stringifyStyleMap.test.ts
index 7a85ba9..1f87ba4 100644
--- a/src/__tests__/stringifyStyleMap.test.ts
+++ b/src/__tests__/stringifyStyleMap.test.ts
@@ -27,21 +27,34 @@ describe("stringifyStyleMap", () => {
     );
   });
 
-  it("doesn't change CSS-selector string", () => {
+  it("makes CSS-rules with CSS-selector string and CSS-properties string", () => {
     const expected =
-      "header{color:teal;} .className{color:teal;} body ul > li{color:teal;}";
+      "header{color:teal;}.className{color:teal;}#root{color:teal;}";
     const actual = stringifyStyleMap({
       header: cssProperties,
       ".className": cssProperties,
-      "body ul > li": cssProperties,
+      "#root": cssProperties,
     });
 
     expect(actual).toBe(expected);
   });
 
-  // TODO: add reducing feature to stringifyStyleMap
-  it("doesn't reduce styles for empty cssProperties", () => {
-    const expected = "header{color:teal;} main{} footer{color:teal;}";
+  it("trims CSS-selector string properly", () => {
+    const expected =
+      ".className{color:teal;}#root div h1{color:teal;}#root>ul li{color:teal;}*>p+ul li{color:teal;}div~p.className{color:teal;}";
+    const actual = stringifyStyleMap({
+      " .className  ": cssProperties,
+      "#root   div h1": cssProperties,
+      "#root >  ul li": cssProperties,
+      "* > p+  ul li": cssProperties,
+      "div ~p.className": cssProperties,
+    });
+
+    expect(actual).toBe(expected);
+  });
+
+  it("reduces styles for empty cssProperties", () => {
+    const expected = "header{color:teal;}footer{color:teal;}";
     const actual = stringifyStyleMap({
       header: cssProperties,
       main: {},
@@ -50,4 +63,18 @@ describe("stringifyStyleMap", () => {
 
     expect(actual).toBe(expected);
   });
+
+  it("injects the '!important' statement for each style property", () => {
+    const expected =
+      "#root{color:teal!important;}.footer{color:teal!important;}";
+    const actual = stringifyStyleMap(
+      {
+        "#root": cssProperties,
+        ".footer": cssProperties,
+      },
+      true
+    );
+
+    expect(actual).toBe(expected);
+  });
 });
diff --git a/src/stringifyCSSProperties.ts b/src/stringifyCSSProperties.ts
index 1d56c5c..456d261 100644
--- a/src/stringifyCSSProperties.ts
+++ b/src/stringifyCSSProperties.ts
@@ -24,5 +24,5 @@ export function stringifyCSSProperties(
       ([key, value]) =>
         `${camelToKebab(key)}:${applyCssUnits(key, value)}${important};`
     )
-    .join(" ");
+    .join("");
 }
diff --git a/src/stringifyStyleMap.ts b/src/stringifyStyleMap.ts
index 307ddf9..452967a 100644
--- a/src/stringifyStyleMap.ts
+++ b/src/stringifyStyleMap.ts
@@ -1,5 +1,6 @@
 import { type StyleMap } from "./types";
 import { stringifyCSSProperties } from "./stringifyCSSProperties";
+import { trimCssSelector } from "./utils";
 
 /**
  * Converts a `StyleMap` (a map of CSS selectors to `CSSProperties`) into a string of CSS rules.
@@ -18,8 +19,16 @@ export function stringifyStyleMap(
   }
 
   return Object.entries(styleMap)
-    .map(
-      ([key, value]) => `${key}{${stringifyCSSProperties(value, isImportant)}}`
-    )
-    .join(" ");
+    .reduce<string[]>((result, [key, value]) => {
+      if (Object.keys(value).length > 0) {
+        result.push(
+          `${trimCssSelector(key)}{${stringifyCSSProperties(
+            value,
+            isImportant
+          )}}`
+        );
+      }
+      return result;
+    }, [])
+    .join("");
 }
diff --git a/src/utils/index.ts b/src/utils/index.ts
index 7042799..63b3aaa 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -1,3 +1,4 @@
 export * from "./camelToKebab";
 export * from "./isUnitless";
 export * from "./applyCssUnits";
+export * from "./trimCssSelector";
diff --git a/src/utils/trimCssSelector.ts b/src/utils/trimCssSelector.ts
new file mode 100644
index 0000000..9a203e4
--- /dev/null
+++ b/src/utils/trimCssSelector.ts
@@ -0,0 +1,6 @@
+export function trimCssSelector(selector: string) {
+  return selector
+    .replace(/\s*([+~>])\s*/g, "$1")
+    .replace(/\s{2,}/g, " ")
+    .trim();
+}